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THE DIURNAL COURSE _/£*/. 
OF EFFICIENCY 



BY 

HOWARD D. MARSH, Ph.D. 



ARCHIVES OF 
PHILOSOPHY, PSYCHOLOGY AND SCIENTIFIC METHODS 



EDITED BY 

J. McKEEX CATTELL and FREDERICK J. E. WOODBBIDGE 



NO. 7, JUET, 1906 



Columbia University Contributions to Philosophy and Psychology, Tol. XIV, No. 3. 



NEW TORK 
THE SCIENCE PRESS 






i>> 



PRFS9 OF 

The New Era Printing Company 
Lancaster, Pa. 



TABLE OF CONTENTS 



PAGE 

Part A. Introduction 1 

Part B. Diurnal Course of Psychophysiological Effi- 
ciency 4 

I. Vital Activities 4 

1. Secretion, Urination, Evaporation 4 

2. Circulation, Respiration, Temperature 4 

3. Deaths relative to Time of Day 9 

4. Brief Summary 13 

II. Sensory Activities 13 

1. Sight, Color-sense, Hearing 13 

2. Skin-sensitivity, Pressure-sense 14 

3. Brief Summary 14 

III. Motor Activities 14 

1. Subhuman Data 14 

(1) Plant Life 14 

(2) Animal Life 15 

2. Human Data 15 

(1) General Characteristics of Writer's Methods and 

Experiments 15 

(2) Actual Tests and Results— Writer's and Others' 17 

a. Speed and Accuracy of Movement 17 

&. Normal Muscular Power 24 

(a) Small and Large Muscular Groups 24 

(&) Comparative Functioning of Such Groups 31 

(c) Bilateral Symmetry 31 

c. General Motor Control 32 

d. Complex Motor Activity— Athletic Perform- 

ances and Manual Labor 32 

3. Brief summary 40 

iii 



iv C0N1ENTS 

PAGE 

Part C. Diurnal Course of Mental Efficiency 42 

I. The Simpler Mental Activities 42 

1. Attention 42 

2. Discrimination — Letters and Forms 44 

3. Association— Reaction-time, Naming Colors, Word 

Associations 46 

4. Memory (mechanical) —Visual, Auditory, Visual- 

auditory 50 

II. The More Complex Mental Activities 53 

1. Arithmetic— Addition, Mental and Written Multi- 

plication 53 

2. Translating French ; Scoring Death Records 55 

3. School Examinations and School Marks 57 

4. Students' and Authors' Preferred Hours for Work 59 
III. Brief Summary 69 

Part D. Chief Causal Factors in the Diurnal Efficiency 

Curve 71 

I. Night-day Rhythm — Sleep and Activity 71 

II. Habits, Meals, etc 74 

III. Fatigue and Feelings of Fatigue 77 

1. Muscular Fatigue 78 

2. Mental Fatigue 78 

(1) Measured by Motor Inefficiency 78 

(2) Measured by Sensory Inefficiency 79 

( 3 ) Measured by Mental Inefficiency 82 

IV. Inertness and Nervousness 88 

V. Sex and Age 90 

VI. Brief Summary 91 

Part E. Conclusion 93 

Bibliography 97 



THE DIURNAL COURSE OF EFFICIENCY 

A. INTRODUCTION 

Recurrence of phenomena is the source of all scientific knowl- 
edge. Rhythmic recurrence in nature is well known; for physics, 
it is perhaps the most general and fundamental characteristic, under- 
lying the theories of the mechanics of motion, sound, heat, light and 
electricity. The student , of astronomy finds the movements of 
heavenly bodies marked by like repetition. It appears in biology 
in a less regular way in the growth changes of vegetable and animal 
bodies and in a more general way in the successive generation of 
species ; while evolution as a whole is rather completely expressed in 
alternation of integration and disintegration. Social life, in all its 
historic aspects, gives evidence of epochal development, and some 
sociologists have gone so far as to make repetition (as imitation, etc.) 
the warp of the whole social fabric. 1 Nearer the point of the 
present research are particular seasonal changes in individual life 
— yearly, quarterly, monthly, weekly, daily — of whose existence we 
have hints in various anthropological, physiological and pathological 
data, more or less closely connected with the sexual, religious and 
emotional life. 2 

This paper deals only with the question whether there are nor- 
mally recurring variations of ability at different periods of the day. 
The discussion of this question is not to be found in general works 
on psychology, however modern, but in sundry monographs and 
journal articles appearing in the last fifteen years. This means that 
the more conservative psychologists are not yet ready to accept such 
recurrence as a fact. But the investigators themselves seem to 
consider it quite confirmed, despite the disagreements of their results 
when intercompared. 

Part of this assurance may be due to ignorance of what others 
have found. The good side of this is that experimentation under 
such conditions has less tendency to bias, to which workers in indi- 
vidual psychology are perhaps more exposed than are those in other 
parts of the experimental field. We want not only the subjective 

1 For complete theory, see G. Tarde's Laws of Imitation and other social 
writings. 

2 Of course there is no doubt about the monthly rhythm in females. For 
other suggested ones, see H. Ellis, The Psych, of Sex, 2. 1902. 



2 DIURNAL COURSE OF EFFICIENCY 

satisfaction, but also the objective recognition, of having obtained 
results with a definite pointing— which 'show something'. But that 
this should be exhibited from the negative side seems often as objec- 
tionable to the searcher as discovery of no 'general tendency'. 

The writer aims to present all the important work hitherto pub- 
lished, having direct bearing on the problem. On account of the 
scope of the latter, no collection of this material at any one point 
is attempted, but it is introduced where most pertinent. The 
greatest lack in all this work lies in two things— inextensiveness of 
the experimental series and omission of quantitative expression of 
the reliability of the results. 

It is easy to account for the first of these deficiencies when one 
remembers the nature of the problem, affecting as it does the whole 
duration of the day. This makes it hard indeed to secure persons to 
act as subjects. If the tests are short, they must be repeated on a 
great number of days, in which case the various conditions must be 
so much the longer controlled; if they are individually more ex- 
tended and adequate, they demand most of the subjects' time for the 
days on which they are taken, and in this case accidental disturb- 
ances are more costly. Therefore the investigator is inclined to 
reduce either the number of days, the number of periods per day, 
the number of trials per period or the number of subjects tested. 

This being true, the second lack mentioned is easily explained. 
The neglect to calculate the averages obtained— a very serious omis- 
sion when differences are small and results not always harmonious— 
arises partly from the feeling that the material at hand is too meager 
to justify the calculus of probabilities. An additional difficulty is 
that in a series of tests day after day the curve of diurnal variation 
is complicated with the curve of progressive improvement due to 
practise. This makes it especially hard to calculate the reliability 
of the averages for the different hours of the day. And even the 
mere labor of the tests and computations is a deterrent; for it is 
clear that if 500 trials are thought necessary to establish a reliable 
measure of any function, ten times that many and ten times the cal- 
culations will be required to establish it for ten periods of the day. 
Other minor deterrents might be enumerated that operate in certain 
cases. 

One other occasion for criticism of the works referred to is found 
in the fact that the tests for the different parts of the day have not 
always been made on the same day. Such procedure implies the 
belief that the absolute ability one exhibits on one day is the same 
as he would manifest at the same hour the next day or any subse- 
quent one : it takes no account of accidental influences, practise 



INTRODUCTION 3 

effects and other inherent factors of change. To keep clear of these 
errors, the tests for the different hours of the day should be made 
on the same days. 

My own work is not free from the first of these criticisms, but 
avoids the remaining two. 

In addition to presenting the work of others, the author, by a 
great variety of extended tests upon himself, has been able to estab- 
lish definitely the course of diurnal changes for one normal subject. 
Six male graduate students, one female graduate, and a group of 
sixteen female undergraduates were likewise employed for both 
motor and mental tests, and the measurement of the hourly product 
of 22 female factory operatives contributed additional data. The 
tabulation of human deaths for time of day; the results of school 
examinations and recitation marks for different diurnal periods; 
the best times of day for athletic performance and for intellectual 
composition; in short, as wide a class of pertinent matter as could 
be secured has been applied to the solution of the question of diurnal 
changes of efficiency. 

In the experimental portion of the present work, much use has 
been made of tests variously employed by others. The aim has been 
to get such variety as the practical limitations of application would 
allow. It is not thought that together they give a measure of 'gen- 
eral intelligence' or 'general motor power'. These themselves have 
rather a precarious existence since analytical psychology has taken 
an experimental turn. Our activities are recognized as much more 
complex than they seem, and tests of them, on the basis of simplicity, 
may not be productive of the most valuable knowledge. Especially 
is this true of adults, to whom my own tests were chiefly confined. 
Still it is true that legitimate and interesting results have been 
reached in the past and that accruing experience must make future 
efforts more fruitful. As the total outcome of. his research, the 
author is not prepared to 'say the last word' about diurnal rhythms, 
but hopes that something worth while has been attained. 

Acknowledgments are due to Professor Cattell for the original 
proposal of the problem and for other suggestions; to Professors 
Thorndike, "Woodworth and Meylan, of Columbia University, for 
assistance of various kinds; to those who acted as subjects at much 
personal inconvenience ; to certain officers and employees of the 
manufacturing firms of Dennison and Sons, J. English and Sons 
and the Trow Directory Company, of New York City, for courtesies 
extended during observational work in their respective factories ; 
to Dr. Guilfoy, registrar of the City Health Department; and to 
other individuals who contributed in different ways. 



B. THE COURSE OF PSYCHOPHYSIOLOGICAL 
EFFICIENCY 

I. Vital Activities 

Any strict line of demarcation between so-called physical and 
mental life does not exist in reality and is maintained primarily for 
convenience in dealing with the complex phenomena of life. For 
the data to be presented in this section the term psychophysiological 
seems best, since from the physical side only the functional aspect 
is dealt with. What will be called 'vital' activities are on the mental 
side directly concerned with emotion ; ' sensory ', with cognition ; and 
'motor,' with volition, as the words are commonly accepted. The 
idea is not to support a three-faculty psychology nor to stand sponsor 
for a rigid meaning of the terms employed. But a more systematic 
presentation of the subject can be given by adherence to the order 
named. 

Considering the length of time that medicine has been studied, 
or even that physiology has been a separate science, one would ex- 
pect to find the matter of physiological rhythms fully discussed. 
However, the text-books here are as barren as those in psychology 
with respect to the general problem. The first and only systematic 
collection of results was published by Vierordt in 1888 1 . The actual 
work was done by various medical men between 1840 and 1880, and 
much of it must be considered unreliable, particularly where the 
conditions of experimentation or observation are not stated. Only 
such figures as seem most trustworthy will be quoted. 

1. Secretion, Urination, Evaporation 

Vierordt 's results here have no value in themselves without fuller 
information as to number of subjects and their habits of life, their 
age, sex, health, etc., together with the length and method of experi- 
mentation. The following are less deficient in these respects. 

2. Circulation, Respiration, Temperature 

1. Circulation. — The most commonly accepted view with regard 
to pulse rate is that the maximum occurs in early morning, followed 
by a steady decline till after midnight, broken only by the temporary 

1 Daten und Tabellen. 1888. 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 5 

influence of meals and accidental excitements. This seems only 
partly true. The correctness of the first statement is greater the 
nearer to arising the record is taken, as will be indicated below. 
The following table gives most of what material could be gathered 
on this matter, together with some of my own. 

Table I. Pulse Rate and Time of Day. 





7 A.M. 




8 9 10 11 12 1 P.M 


2 3 4 




5 6 7 




8 


9 10 


11 12 


1 






* 74 71 70 69 81 


84 82 77 




78 75 75 










2, 






68 * 71 


68 




68 






*72 




2., 






73 * 83 


76 




68 






*69 




2, 






90 * 105 


97 




82 






*97 




3 


68 


* 


81 87 73 79 67 82 


83 73 73 




70* 85 










4, 






56 * 72 






69 


# 






65 


4, 


72 


* 


86 83 81 76 73 79 


77 75 72 




78 * 84 82 




77 


73 70 


69 68 


4, 


71 


* 


78 74 70 77 


72 


70 


72 * 


7S 




76 71 




4, 


84 


* 


94 98 84 78 77 * 


82 76 




*86 






72 





1 — Vierordt. Self, number of days not stated. 

2 — Binet. 2 1 self, 7 days; 2 2 male adult, 2 days; 2 3 female adult, 2 days. 
3 — Storey. Self, average of 6 to 10 determinations. 

4 — Marsh. 4 t male adult, 6 days; 4 2 male adult, 15 days (summer) ; 4 3 
same, 12 days (winter) ; 4 4 female adult, 7 days. 
* — Indicates occurrence of meals. 

Not all the series approach completeness. Small dependence 
can be placed on l 1 ; Binet 2 says of his own that ' ' they are three 
single curves chosen from a great number because of the distinctness 
of the tracings", not saying that they are even representative ones; 
4 X is a short series but with small probable error. 

The first four and 4 X show the maximum rate at about 1-2 p.m. 
(2 also at 9 p.m.), the others at 8-9 a.m. The changes to which we 
are subjected on awakening act as excitants and largely cause the 
apparently high early morning rate. Change of position alone has 
great influence. Ten mornings, in my own case, the rate two minutes 
after arising averaged 81, as compared with 72 twenty minutes later ; 
and again in the second series the figures were respectively 81 and 
71. Subject 4 4 did the same thing a like number of days, taking an 
additional record in bed several minutes before arising. Her aver- 
ages were 79, 87 and 84. These facts suggest what small reliance 
can be placed on bare pulse figures in tables. What seems to be 
true here, aside from the doubly induced increase due to rising and 
eating, is first a morning rate less high and less well sustained than 
the afternoon rate; second, a higher female than male rate, with 

1 Yet, as late as 1900, the Am. Text-book of Physiol, quotes these figures as 
bases for conclusions. This shows how meager is the information. 

2 ' Le Changements de Forme du Pouls Capillaire,' L'Annee Psych., 3. 1897. 



6 DIURNAL COURSE OF EFFICIENCY 

tendency to an earlier maximum 1 ; and third, a general rate higher 
than the 70 so long accepted as about the average. 

As to the first point, the order is sustained by a recent study of 
blood and pulse pressures made by Erlanger and Hooker 2 with one 
adult subject. Five extensive tables show the results obtained for 
five days, at different hours from 8 a.m. till 10 :30 p.m., but their 
reproduction here is forbidden by their great length and uncertain 
value. However, the authors draw this conclusion: "We therefore 
can distinguish a gradual increase of pulse-pressure [directly pro- 
portional to pulse-rate according to them — p. 294] throughout the 
day upon which is built up the wave-like increase that follows upon 
the ingestion of meals" (p. 343). "There seems to be no relation 
between the amount of food ingested and the height and duration 
of the post-prandial [fundamental] rise" (p. 344). 

In addition to this direct evidence there are other facts in favor 
of the view that the pulse is normally lower in the morning than 
later in the day. Muscular and brain activity heighten the pulse 
rate on account of the increase in waste products sent to the heart. 
If it be true that a greater muscular power accompanies increased 
rate of circulation, as shown by Zablondousky 3 and Maggiora 3 with 
massaged muscles, and by Kronecker 3 with injection of blood into 
fatigued muscle, then, according to the traditional pulse theory, the 
greatest strength might be expected in the early morning. As a 
matter of fact, it is probably least then, as will be shown later. 

Periodicity in pulse intensity and blood pressure, dicrotism and 
the rapidity of vascular reflex have been investigated, but the results 
are unimportant. 

2. Respiration. — One expects to find a positive correlation • be- 
tween pulse rate and respiration and temperature, as they have a 
common dependence on the amount of metabolism in the body, the 
latter in turn being largely proportional to the excitement or activity 
at any period. And it is found to be so in fact. 

Vierordt's maximum for himself was at 2 p.m. for rapidity of 
respiration and volume of air and of C0 2 expired, and minimum at 

1 The high night rate of 2 3 is due to the evening meal and no comparable 
morning figure is shown, while the case of 4 4 shows a considerable falling off 
towards night. Guy and Knox, per Vierordt, found a higher rate for children 
with an early morning maximum.. Miss N. Norsworthy, of Teachers College, 
in a recent research, the results of which are as yet unpublished, found for 
girls under 15 years a rate of 95.5, and above 15, of 93 — 295 cases; for boys 
under 13, 95, and above 13, 85 — 253 cases. 

2 ' An Experimental Study of Blood-pressure and Pulse-pressure in Man,' 
Johns Hopkins Hosp. Reps., 12: 145-378. 1904. 

3 J. Joteyko, ' Revue Generale sur la Fatigue Musculaire,' L'Annee Psych., 
5. 1898. 



COVRSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 7 

7 p.m. — the last hour of his series. Binet's maximum occurred at 
7-9 p.m. and minimum at 8 a.m., his series being from 8 a.m. to 
8:40 p.m. Tigerstedt 1 (after Jiirgensen — see Fig. 1) finds the 
maximum volume of CO, at 5-8 p.m. and minimum at 4-8 a.m. 



?.M. 




Fig. 1. Normal Variations in Body Temperature (after Tigerstedt). 

Johannson 2 finds that the greatest quantity of CO, is given off 
by an active subject from 8-12 a.m. and the least from 4-6 a.m. ; 
this was practically true also during perfect rest. His experiments 
were on himself, in six-hour courses of activity and, again, of in- 
activity (in bed), requiring different days to cover the whole twenty- 
four hours. 

In accord with this evidence are certain data obtained from 
spirometric tests of Filipinos at the St. Louis Exposition, 3 where 
72 were tested for lung capacity in the morning and 41 in the after- 
noon. The average for the morning was 170.0 cu. in., with a prob- 
able error of 1.76 ; and for the afternoon, 177.2, with P.E. 2.60. In 
my own case, eight trials at each period showed averages as follows : 

7-8 A.M., 189; 9-10 A.M., 192; 11-12 A.M., 191; 1-2 P.M., 188; 3- 

4 p.m., 192 ; 5-6 p.m., 192 ; 7-8 p.m., 193 ; 9-10 p.m., 191. This fol- 
lows closely the curve of my motor ability as found by many tests. 
3. Temperature.— Reference to Table II. and Fig. 1 makes it 
evident that the temperature reaches the highest point about 5- 
8 p.m. and the lowest about 7 a.m. Johannson finds the same true 
for diurnal activity or rest conditions. Attention is called to the 
close similarity of the curves in Fig. 1, and to the close agreement 
of the results cited. 



1 Lehrbuch der Physiologie. 1902. 

2 ' Ueber die Tagessehwankungen des StofTweehsels und der Korpertemper- 
atur, Skand. Archiv. fiir Physiol., 8. 1S98. 

3 Fuller reference to this work will be made later. 



DIURNAL COURSE OF EFFICIENCY 
Table II. Body Temperature and Time of Day. 





6 A.M. 


7 


8 


9 


10 


li 


12 


1P.M. 


2 


3 


4 


5 


1, 






37.9 


* 








*38.4 






38.2 




1, 






37.5 


■X- 








*37.9 






37.8 




2, 




36.4 


36.7 


* 


37.0 


37.2 


37.1 




*37.3 






37.5 


2, 




36.6 


36.8 


* 


37.1 


37.1 


37.1 




*37.2 






37.3 


3, 


33.3 


32.8 


32.9 


32.5 * 


32.5 


33.6 


34.2 


*35.5 


34.5 


33.5 


33.9 


33.2 


3 2 


36.4 


36.9 


37.2 


37.2 * 


37.3 


37.4 


37.4 


*37.5 


37.4 


37.4 


37.4 


37.4 




6 P.M. 


7 


8 


9 


10 


n 


12 


1A.M. 


2 


3 


4 


5 


1, 




38.4 




*38.5 


















1, 




38.0 




*38.2 


















2, 




37.4 




*37.2 




36.9 














2, 




37.1 




*37.1 




36.7 














3, 


34.2 


35.6 


36.0 


35.9 


35.8 


35.7 


35.7 


35.5 


35.2 


34.7 


35.0 


35.0 


3 2 


37.5 


37.5 


37.4 


37.2 


37.0 


37.0 


36.8 


36.8 


36.7 


36.6 


36.6 


36.4 



1 — Binet. \ x hand; 1 2 rectum; self, number of days not stated. 

2 — Vierordt. 2 ± average of Jiirgensen, Liebermeister, Barensprung — 
rectum — days not stated; 2 2 average of Gierse, Hallmann, Lichtenfels, Friihlich — 
mouth — days not stated. 

3 — Roemer. 3 ± hand; 3 2 rectum; subjects and days not stated. 

* — Indicates the occurrence of meals. 

Some very interesting experiments by Galbraith and Simpson 1 
on the temperature wave in the monkey may be briefly described 
here. The axillary temperature of six subjects was taken every 
two hours, day and night, under different conditions, as follows : 

(a) Twelve days — ordinary conditions — fed at 9 a.m. and at 
6 p.m. — period of activity, 9 a.m. to 9 p.m. ; of rest, 9 p.m. to 9 a.m. 
Result : rise during activity, maximum at 5 p.m. ; fall during rest, 
minimum at 6 a.m. This occurred every day. 

(6) Six days — conditions exactly reversed (artificial light at 
night)— fed at 6 a.m. and at 9 p.m. Result: complete reversal of the 
diurnal wave in 24 hours; maximum at 2 a.m. and minimum at 
5 p.m. 

(c) Six days — active from 3 p.m. to 3 a.m., etc. Result: similar, 
though slower, modification of the wave; maximum at 9 p.m., mini- 
mum at noon. 

(d) Six days — in darkness during entire time, etc. Result: wave 
became irregular, then gradually disappeared. 

(e) Six days— in light whole time, etc. Result: no wave shown, 
but an irregular curve; animals irritable. 

To verify these results, experiments on birds were next under- 
taken. 2 The owl reached the maximum at night and the minimum 

1 ' Conditions Influencing the Diurnal Wave in Temperature of Monkey,' 
Jour, of Physiol., 30, 2: 20; Proc. Physiol. Soc. 1903. 

2 ' Temperature Variations in Nocturnal and Other Birds,' op. cit. 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY Q 

in daytime. The thrush, on the other hand, reached these points at 
noon and midnight, the difference amounting to over 5 degrees centi- 
grade. Gulls, pigeons and three varieties of ducks showed similar 
variations ; the smaller the bird the greater was the diurnal variation. 
The recurrent rhythm of day and night and the consequent 
habitual alternation of activity and rest are seen to be the all- 
important factors here, as they are also, probably, for men. Unfor- 
tunately, no analogous human experiments have yet been made. 

3. Deaths Relative to Time of Day 

Kirkpatrick, 1 discussing fatigue, makes the remark (p. 327) that 
since more deaths occur about 4 a.m. than any other hour, vitality 
is then probably lowest. He cites no authority for this statement, 
nor has the writer been able to locate any in print, though it appears 
to be widely accepted as a fact, even by physicians who have been 
personally questioned. To determine the facts 36,000 records of 

Table III. Deaths Relative to Time of Day. 



Description of 
Group. 


Total 
No. 


6 A.M. 


7 


8 


9 


10 


11 


12 IP. M. 


2 


3 


4 


5 


Zymotic cases — 


15,616 
23,439 
11,991 
11,448 


660 659 

1003 1007 

493 525 

510 482 

227 211 
113 137 
268 272 
241 229 
154 158 

369 359 
358 381 
276 267 


579 
953 
491 
462 

209 
115 

245 
237 
147 

348 
373 
232 


631 
959 
506 
453 

171 
130 
261 
248 
149 

360 
339 
260 


628 
970 
501 
469 

178 
122 

272 
238 
160 

380 
325 

265 


668 
981 
501 
480 

195 
125 

264 
242 
155 

330 
372 

279 


665 

782 
409 
373 

152 
96 
229 
185 
120 

270 

269 
243 


598 
955 
484 
471 

176 
117 
268 
239 
155 

324 
336 

295 


695 687 697 
980 1009 1006 
471 505 500 
509 504 501 

202 203 180 
123 105 122 
275 296 286 
239 253 247 
141 152 166 

312 371 372 
375 357 351 

293 281 278 


693 
1054 




m?, 




49? 


Age— M. & F. 
1- 5 


203 


6-25 


119 


26-45 


9,78 


46-65 


?76 


66-95 


183 


Season, M. & F. 
Nov. -Feb 

Julv-Oct 


361 

378 
315 



Description of 
Group. 


Total 
No. 


6 P.M. 


7 


8 


9 


10 


11 


12 1A.M. 


2 


3 


4 


5 


Zymotic cases — 




709 
994 
530 
464 

201 
119 
256 

272 
146 

325 
354 
315 


623 
948 
493 
455 

181 
94 
275 
245 
153 

324 
351 
273 


603 

984 
520 
464 

181 
135 
267 
249 
152 

375 

319 
290 


634 
947 
492 
455 

200 
127 
263 
208 
149 

336 
333 

278 


688 723 
9421107 
471 540 
471 567 

162 219 
127 135 
263 281 
238 300 
152 172 

327 434 
331 377 

284 296 


412 669 
847 1026 
441 514 
406 512 

138 200 
98 122 
248 285 
201 286 
162 133 

323 410 

276 318 
248 298 


624 
994 
490 
504 

211 
130 
250 
258 
145 

379 
332 

283 


651 

981 
532 
449 

190 
107 
301 
245 
137 

348 
332 
301 


660 

986 
485 
501 

190 
114 

268 
244 
172 

361 
359 
266 


663 
0?9 




535 




494 


Age— M. & F. 
1- 5 


213 


6-25 


130 


26-45 


W2 


46-65 


^53 


66-95 


In? 


Season, M. & F. 
Julv-Oct 


383 

369 

277 



Fundamentals of Child Study. 1903. 



10 



DIURNAL COURSE OF EFFICIENCY 



deaths occurring in New York City in 1901 were worked over by the 
writer. Those cases were excluded in which death was caused by 
suicide or accident, those of children under one year in age, and 
those where the hour was omitted from the doctor's certificate. 
Males and females were recorded separately and in the following 
age groups: 1-5, 6-25, 26-45, 46-65, 66-95. Three seasons of the 
year were also noted: November-February inclusive, March-June, 
July-October. For each of the months 3,000 cases were used, but 
after making the above exclusions only 23,439 remained. In addi- 
tion to these, Table III. reports 15,516 deaths from zymotic diseases, 
which had been tabulated for each hour of the day in the official 
records of the city Health Department for the years 1876-79. No 
others were found for subsequent years, up to date. In all but the 
first group 6 a.m. means from 5:30 to 6:30; what it means in the 
first group was not discovered. 



A.M Noon 



PM Mn-MCHT sAA4. 



i?(Y) F, 7 R .o in i7~l? i 2 ,? 4 s f, 7 ft a /o // 7? / 2 ■? f J-6/foa 




v Females -Broken L/ne 

Figures at the sides indicate number of cases. 
Fig. 2. Deaths Relative to Time of Day — see Table III. 

This table and these curves of the chief groups are by no means 
easy of interpretation as they stand. This is mainly due to one 
peculiarity, affecting every group, which must first of all be ac- 
counted for if possible. This is the notably apparent decrease in 
deaths at the noon and midnight periods. Its occurrence at these 
particular points is prima facie evidence that a real fact is not dis- 
closed, and its occurrence in all groups is convincing proof of some 
external cause. It can probably be explained if Kant's philosophic 
theorizing be allowed— that 'man is by nature lazy'. This seems a 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY H 

far cry to the present matter, but a few words will make it plain. 
The attending- physician must certify, as to the hour of a patient's 
death, that so-and-so died 'at — m.' This works happily enough till 
the periods in question are involved, when immediately arises the 
necessity of writing out in full the words 'noon' and 'midnight' for 
the sake of their clear distinction. 1 Rather than take this trouble, 
the indifferent doctor will do one of two things — either leave the 
space blank or make the record for the closely preceding or suc- 
ceeding hours. In the first event a like loss is occasioned in the two 
periods, since the record does not then differ from those left blank 
for other reasons, all of which records had to be excluded. The 
cases thus affected would account for only a small part of the ap- 
parent decrease — possibly one tenth. In the other event, the ad- 
jacent periods should show decided increase. That is precisely what 
they do at midnight, sufficiently to smooth the curves from 10 p.m. 
till 2 a.m. inclusive, as indicated by the dotted lines in Fig. 2. It is 
not so evident at noon, and there may be a real decrease at that hour 
— a possibility somewhat emphasized by the 1 o'clock drop in the 
first group. 

The first two curves are similar throughout, save at noon. When 
corrected as suggested they are easier to compare. The highest rate 
in each occurs, not at 4 a.m., but from 2 to 6 p.m. ; and the minimum, 
less well marked, immediately after — from 7 to 12 p.m. An exam- 
ination of the figures of the sex group shows much the same order, 
the females reaching a slightly earlier maximum than the males, 
while 3 a.m. and 5 p.m. are the only points of notable opposition. 
The female rate is more regular than the male. In the age group, 
26-45 most resembles the female curve and 46-65 the male. In the 
season group, the July-October curve most nearly follows that for 
all deaths. 

Just what these results mean is puzzling. The differences are 
frequently much above those easily accounted for by chance. While 
the number of cases seems large, it is only about one fourth large 
enough. The sub-groups for age and times of year are far from 

1 This would not be the ease if many people, including doctors, did not 
think that M stands for midnight as well as for meridian, while some think 
it stands for nothing else. The first set of figures is seen, relative to the 
second, to show a much less noon and a much greater midnight drop. This 
is best accounted for by supposing that the compiler included at the former 
period all cases marked ' 12 M.,' whereas part doubtless belonged to the latter 
period. The same is less true of the second set because some of these cases 
were distributed to the later period. Attention is called to the fact that these 
points are disregarded in the ' smoothings ' shown in Fig. 2, but should be 
remembered in connection with the further discussion of the curves. 



12 DIURNAL COURSE OF EFFICIENCY 

being extensive enough to throw adequate light on the causal factors 
involved. Even after combining the male and female figures, each 
period of these groups is poorly represented ; but such a combination 
is scarcely allowable. Confining attention to the first three groups, 
the venture of a definite opinion might be hazarded. 

At first thought one would be tempted to infer from the occurrence 
of the maximum at the warmest part of the day, that the heat was 
the important factor. But inspection of the seasonal figures shows a 
much lower death rate in July-October than in winter, while the 
curve for the summer months closely resembles the general curve. 
Heat alone offers no solution. 

The following theory is more in harmony with the facts : the 
vast majority of these people died of disease and not of old age. 
The proportion of sudden to gradual deaths was, on the whole, small. 
The 'average patient' (to generalize for adults) on awakening is 
fed, and for an hour his death rate is lowered, food influence being 
often eked out by a nap. His waking troubles begin thereafter and 
cause a rise in the rate till at noon he is again fed and reduced to a 
minimum of activity for an hour or two. Then the troubles and 
frettings are resumed more vigorously, the body having now become 
thoroughly 'warmed up', and the actions responsive to this increased 
state of stimulation sap the energy more rapidly, till the final sur- 
render takes place about 5 or 6 p.m. For the survivors, there is at 
this time another meal and consequent lowering of the curve, which 
is again emphasized by longer sleep, during which there is a gradual, 
slight rise in rate till the morning awakening. 

This idea is supported by the time of occurrence of the highest and 
lowest rates in the age groups. A close scrutiny, with the suggested 
smoothing always in mind, reveals that the maximum for ages 1-5 
is very early in the morning — before 9 ; that for 6-25, from 7 to 
11 a.m. ; that for 26-45, about 3 to 4 p.m. ; and for the following 
years, about 5 to 6 p.m. The curve of diurnal activity probably 
varies rather similarly with age. A large increase in the number of 
cases would be of marked value, as it is evident that these groups 
are not only too wide, but are also rendered too heterogeneous by the 
sex element. The minimum locations are likewise confirmatory, as 
they uniformly occur at the customary points of least activity — 
meal-times and night. 

At all events, the 4 a.m. idea is effectively exploded. The cases 
are numerous enough to establish this point reliably. The females 
of the second group show a drop at 3 a.m., which is offset by a male 
rise and hence a straight line appears in the curve of the whole 
group for this part of the night. As a matter of fact, the time from 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 13 

1 to 5 a.m. is but a trifle higher in death rate than the median for 
the whole day. The body temperature and expiration of C0 2 , as 
shown by Fig. 1, would lead one offhand to expect the greatest num- 
ber of deaths about 4 or 5 a.m. The fact that they do not come at 
this point of apparently lowest vitality, throws us back to the con- 
clusion already drawn. It appears paradoxical to call the point of 
greatest strength — a fact to be later demonstrated— the most likely 
death point, yet it is really not unreasonable. It is well known that 
patients usually grow worse towards evening. The successive mo- 
ments of pain or chafing throughout the day act in a cumulative 
way physiopsychologically, causing increased irritation, which ex- 
cites to the expenditure of more energy than the system can afford 
to lose. 

4. Brief Summary 

It may be said that, in a general way and ignoring the immediate 
effects of meals as far as possible, the heart and lung functions and 
body temperature tend to vary alike, beginning with a very early 
minimum — about 5 a.m. — and increasing to a late afternoon maxi- 
mum — about 5 p.m. There is ground for believing that women reach 
an earlier maximum than men, at a higher rate, and children a still 
earlier maximum at a still higher rate. Similar facts seem to hold 
good in the case of animals, where it is found that the periods of 
rest and activity determine the curve entirely. While the same 
maximal period holds for human deaths, the minimal one is from 
7 to 11 p.m., females again coming to an earlier maximum than males, 
and young children to a very early one. Contrary to what one 
would anticipate, the maximal death rate in each of these groups 
falls very near to the time where we are led in normal life to look 
for the greatest physical efficiency, as evidenced by muscular power. 
This is most likely due to the fact that, in the main, at these periods 
the most effective stimuli are in operation, externally and internally, 
and cause an over-expenditure of energy from which it is impossible 
for many patients to rally. While a sort of physical weakness prob- 
ably exists very early in the morning, it is not true, as held by pop- 
ular opinion, that we are 'nearest death' at that particular portion 
of the day. 

II. Sensory Activities 
1. Sight, Color-sense and Hearing 

In some psychological experiments on various peoples at the 
St. Louis World's Fair, in which the author assisted those in charge 
of this section of the exposition— Dr. R. S. Woodworth and Mr. F. 
2 



14 DIURNAL COURSE OF EFFICIENCY 

G. Bruner, of Columbia University — the sight and hearing of over 
100 Filipinos were tested between 9 :30 a.m. and 12 m., or between 
2 p.m. and 4 :30 p.m. For acuity of vision the so-ealled E-test was 
used, in which lines of E 's of successively smaller sizes and pointing 
in different directions are arranged on a chart like the ordinary 
letter charts for optical tests, and the greatest distance, at which 
the subject can recognize the positions of the E's in each line, is 
determined. The results give the average ratio of the distances so 
determined to the standard distances. There were 70 cases in the 
morning, giving an average of 1.90, and 38 in the afternoon, aver- 
aging 1.94. That is, the difference is little better than one of chance. 

The same subjects, in matching a series of shades of colors with 
a series of tints, averaged respectively 11.8 and 11.5 errors, thus 
favoring the morning, but only to the chance degree. 

In acuity of hearing, as tested by apparatus devised by Mr. 
Bruner for the purpose, 37 men in the morning showed an average 
ability slightly inferior to that of 23 men in the afternoon. The 
numbers are too small to make this difference significant. 

2. Skin-sensitivity and Pressure-sense 

What work there is here bearing on diurnal variation is best 
discussed under the headings of attention (p. 43 and Table XIV.) 
and fatigue (p. 79 and Tables XXX., XXXI. and XXXII.) . 

3. Brief Summary 

No diurnal changes in sensory efficiency are suggested by the 
scanty data at hand, save a possible low skin-sensitivity in early 
morning. 

III. Motor Activities 

1. Subhuman Data 

1. Plant Life.— The following statements are of some interest for 
comparison with human data. Sachs says, "If a plant, which has 
been exposed to the alternations of day and night, be kept in dark- 
ness for a considerable time, the periodicity (due to light) may con- 
tinue for a time, according to Pf eff er, as a persistent effect. ' n Pierce 
bases the following statements on work by Sachs: "The daily 
periodicity of light and darkness is almost coincident with the 
daily periodicity in growth rates. . . . The rate of growth in length, 
of plants furnished with all the food they need, will reach its maxi- 
mum about sunrise and its minimum about sunset." 2 



1 American Text-book of Botany, p. 883. 1882. 

2 Plant Physiology, v- 211. 1903. 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 15 

2. Animal Life.— Hodge and Aikins, 1 experimenting with one of 
the Protozoa, found the ciliary activity of this animal, by which 
food is injected and detritus ejected, to be apparently without periods 
of rest corresponding to those of higher animals. This constancy 
seems unaffected by reproduction, barometric pressure, light, heat, 
or sound. In their diagram of the activities of the animal, the most 
pronounced vesicular and stalk contractions and reproductive phases 
appear to be recurrent in the early morning. These are of the same 
order as man's motor and reproductive activities, while the uninter- 
mittent character of the ciliary activity is what might be anticipated 
when it is remembered that this undifferentiated functioning in 
these unicellular animals is that which, in developed form, finds ex- 
pression in our unremitting circulatory and respiratory perform- 
ances. With advance up the animal scale the number of rhythmic 
activities slowly increases. 

2. Human Data 

1. General Characteristics of the Writer's Methods and Experi- 
ments. — To determine with scientific exactness the diurnal course 
of any activity would require a minute consideration of the subject 's 
daily physical and mental condition, the character of his daily work 
and habits — as to regularity and irregularity, quantity and quality — 
and of all external and accidental influences to which he might be 
subjected at any period of the day. It would be impossible to ascer- 
tain accurately all these matters, but practically what we want to 
know is what one does accomplish under just such heterogeneous 
circumstances — the ordinary conditions of life. Allowances were 
made for several serious interruptions, and where illness occurred 
the records were not used. 

In order to insure the greatest variety of material, the data were 
gathered not merely from strictly laboratory tests., but also from 
those less capable of exact measurement in standard terms; and, in 
addition, the questionnaire method was attempted and data from 
general and school work utilized. The tests were applied extensively 
to groups of subjects for one or two days, and intensively to indi- 
vidual subjects for several weeks. Some information as to the sub- 
jects, periods and tests used and as to results and their statistical 
treatment must be given. 

Subjects. The males were seven in number, all graduate students 
at Columbia University, ranging in age from 26 to 34, and will be 
referred to hereafter as I., II.- VII. All were conversant with and 
practised in laboratory work ; hence each acted as both operator and 

1 ' Daily Life of a Protozoan,' Am. Jour, of Psych., 6: 524-533. 1895. 



16 DIURNAL COURSE OF EFFICIENCY 

subject in his own case, after full verbal and written instructions on 
every test of his series. The letter 'A' will be used to represent a 
female graduate student, 23 years old, engaged in intellectual work 
10 to 13 hours daily; 'B' is a group of young women of Teachers 
College, ranging in age from 20 to 35. Both A and B were naive 
subjects, and their tests were given by myself. 

Periods. The tests were to be taken daily before breakfast, lunch, 
dinner and bedtime. The actual times at which they were taken 
necessarily varied somewhat for different persons, this being one of 
the great practical difficulties of the problem. To get reliable results 
one must start with reliable subjects, but they are just the ones who 
can least afford to distort their affairs daily for so long a time. The 
periods in the tables are two hours broad to allow classification of 
the subjects together. 

Tests. Each subject went through the tests for about twelve 
days; the exact numbers will be indicated in the following pages, to 
which reference must also be made for detailed descriptions of the 
various tests. About six sorts of tests, motor and mental, were given 
to each subject, except that subject I. (the author) took a much 
greater number. But the results of some of the tests admit of 
double measurement — for speed and for accuracy— and appear so 
in the tables. The 'number' given in the second column of some 
tables has reference to the trials at each period and not to the total 
number in the whole series. 

Results and Statistical Treatment. The results are from whole 
days' records, as already suggested. 1 All results are in terms of the 
average and its probable error, the formula used for calculating the 
latter being ± 0.6745 (a/Vn), where o- is the mean square deviation 
and n the number of cases. The mathematical chances are even that 
the average shown will not vary from the real (theoretical) average 
by more than the limits of the P.E. It should perhaps be remarked 
that it was necessary, though less desirable, to have the higher fig- 
ures represent greater degrees of inefficiency instead of efficiency ; 
the larger the numbers, therefore, the less the efficiency. Corrections 
were frequently made for practise effect. There would be no occa- 
sion for this if only averages were sought, but it is absolutely re- 
quired when a figure for their reliability is wanted. The method 
used for eliminating the practise effect was to make an empirically 
graduated scale of allowance for the successive days, which was 
based, as to the whole amount, on the absolute differences between the 
initial and final records and which took advantage, as to graduation, 

1 See p. 3. 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 17 

of the established fact that the effect of practise is at first very pro- 
nounced and then decreases more slowly. There are two assump- 
tions in the method: first, that practise affects all the periods of the 
day equally; second, that any possible correction thus made and 
applied to all the periods alike is legitimate, however low it reduces 
the probable errors, since these will always remain higher than if a 
perfectly adjusted and full correction could be made. The first 
assumption may or may not be true, but it seems to me that no excep- 
tion can be taken to the second. Any correction of a constant error 
is almost sure to be nearer the truth than any uncorrected figure, as 
it is then transferred to the rank of chance where elimination of its 
influence by others is much more likely to occur. When a 'total' 
average in the tables refers to only a few individuals, it should not 
withdraw attention from the separate records themselves, where the 
main truth is then most probably located. 

What has been said above refers also to the mental tests, which 
were taken by each subject at the same times as the motor ones. The 
mass of details to be handled makes the briefest treatment necessary 
at every point, with elimination of repetitions as far as possible. 

2. Actual Tests and Results — writer's and others'. a. Speed 
and Accuracy of Movement. — As a rather simple form of movement 
the subjects were required each period to strike with a pencil point, 
as rapidly as possible, 200 small squares (1 cm.) arranged in 10 
columns of 20 each. The time of performance gives the measure of 
speed, while the number of squares missed roughly indicates the 
(in) accuracy. None of the subjects except the writer knew that 
the accuracy was to be considered. Table IV. shows the results and, 
for convenience of comparison, those of a test treated in the imme- 
diately following sub-section. 

A small correction was made for practise. The greatest defi- 
ciency appears at morning and night periods, a difference that is 
significant, 1 as seen by the P.E.'s of each average and the uniformity 
of the individual results. But the inaccuracy maximum and mini- 
mum seem just the reverse, and this may account for the preceding 
differences entirely or in part. 

The group of young women, B, in taking this test, were allowed 
45 seconds to strike 200 squares or as many of them as possible. The 
results show somewhat the same inverse relation of speed and accu- 
racy and the same order of rate efficiency as the individual cases. 
The improvement here might, however, be attributed to practise. 

1 The exact significance of a difference can be found by various formulae : 
see Thorndike's Mental and Social Measurements, p. 145. But it can be seen 
well enough, often, by inspection of the P.E.'s. 



18 



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COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 19 

Another sort of accuracy test in my own case gave about the same 
result. The so-called hold-and-let-go method was employed in a 
twelve-day series in which a light (4 gr.) wooden disk was snapped, 
on a smooth board, toward an aperture slightly larger, 60 cm. distant. 
This was done ten times per period each day and the inaccuracy 
measured by the average distance at which the disk lodged from the 
hole. These averages for the four periods, which have large P.E.'s, 
were obtained. 

Right 9.3 8.3 7.6 8.7 

Left 12.1 11.4 11.4 12.5 

The middle periods of the day still remain better than the morn- 
ing and evening. 

A more complex movement was tested by having several subjects 
write the numeral words 'one' to 'twelve' five times each period and 
the time taken. Group B wrote as many words as possible in 90 
seconds. The results, in the above table, rather confirm the order of 
deficiency in speed, as found for the simpler movements. 

At the Department of Psychometry and Anthropometry of the 
St. Louis World's Fair many people were subjected to various tests, 
as above mentioned, and their records were kindly put at my disposal. 
Only a part of them could be used for the problem of periodicity. 
Two movement tests were used which need some description (see 
right end of Table V. ) . 

The 'accuracy' test was devised by Dr. Woodworth and consisted 
of an equilateral triangular piece of hard wood into each apex of 
which was inserted a brass circular plate containing a central hole 
6 mm. in diameter and 25 mm. deep. These holes were 12 cm. apart 
and an electrical arrangement was made whereby a bell was rung 
every time a metal 'poker', a trifle less in diameter than the holes, 
was pushed to the bottom of any one of them. The method was to 
hit the holes as rapidly as possible in succession, count being kept 
by the operator of the record made per minute. The accuracy was 
therefore measured in terms of the rate at which the accurate move- 
ment could be repeated. 

The apparatus for measuring the 'rate of tapping' was also of 
an electrical nature. A brass plate, about 10 cm. across, was con- 
nected with a mechanical counter 1 ; the circuit was closed and the 
counter moved forward one point every time contact was made, by 
tapping, between the plate and a short copper rod, held by the sub- 
ject. The time for 100 taps was taken by a stop-watch. 

1 Kindly supplied by the C. H. Stoelting Co., Chicago, 111. 



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COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 21 

A glance at the table of results reveals five groups of males and 
three of females, a separation made necessary by the special condi- 
tions obtaining in each. The Filipino 'band-men' are separated 
from the 'scouts' and 'constabulary' because, being musicians, they 
were a highly selected group, and in fact, as the results show, they 
were much quicker and more accurate, but much less strong, than 
the ordinary soldiers composing the other groups. 1 The first group 
of white males and females comprises individuals taken through a 
long series of tests and measurements, and their records will be 
found much lower than those of the succeeding groups, which were 
taken under highly competitive conditions and only in the activities 
shown. (4), of the males, and (2), of the females, as well as many 
of the Filipino records were taken by myself. 

Since the morning and afternoon divisions of these groups were 
composed of different persons, the practise effect, so troublesome in 
most of my other series, is avoided here. But offsetting that advan- 
tage is the great difference between individuals, which raises the 
variability of each group and diminishes the reliability of the aver- 
ages. The P.E.'s are indeed so large that it did not seem worth 
while to insert them in the table. While no special significance can 
be assigned to the difference between the morning and afternoon 
results of any single group, the general tendency of the whole table 
seems plain. The number of groups in which the afternoon records 
surpass the morning is greater than can reasonably be assigned to 
chance. This tendency to increased motor efficiency in the after- 
noon is slightly less marked in the female groups than in the male. 
As a whole, therefore, these results lean the same way as those in the 
more intensive series. 

Use of the same apparatus by myself gave the results exhibited 
in Table VI. There were two series of tapping tests. The first was 
for twelve days, in each of which the time was taken for 200 taps at 
ten different periods. In a later one for five days, the time of 200 
taps was taken six times at each of seven periods, every 200 alter- 
nating with an accuracy test of the time required to ring the bell 
100 times. 

The thing most worthy of note in this table, aside from the gen- 
eral agreement with the tendencies found above, is the exceptional 
occurrence and decisiveness of the maximum tapping rate at 9- 
10 p.m.— less distinctly manifested in the case of the right hand than 
of the left. The maximum of accuracy clearly comes earlier in the 

1 Of the soldiers, all those shorter than five feet or taller than five feet six 
inches are excluded, because it so happened that a larger proportion of short 
men were tested in the morning and of tall men in the afternoon. 



22 



DIURNAL COURSE OF EFFICIENCY 



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COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 



23 



day than the maximum of speed; a shorter series of accuracy tests, 
with the same subject, tended to place the maximum earlier than 
4 :30 p.m. ; there is no doubt that it falls somewhere in the middle 
portion of the day. 

It is obvious that the rating in accuracy, secured by use of this 
test, has some dependence on the rapidity of the movements involved. 
To see if any change of order would be effected, if the factor of 
speed were eliminated, the following trial was made. 100 dots, 
1 cm. apart, were arranged in ten (printed) rows, both vertical and 
horizontal. By a free-hand, easy and uniform movement, with a 
fountain pen, these rows were successively traced over both hori- 
zontally and vertically, 100 in each direction being done at a period. 
The results are in terms of the average number of dots missed every 
ten lines. 

Table VII. 



No. of 
Rows 



7:30 A.M. 9:30 

Misses. P.E. IMis. P.E. 



100 0.85 .23 
100 2.10.^/ 



11:30 
Mis. P.E. 



1:30 P.M. 
Mis. P.E. 



0.80 .19 0.82 .19 1.11 .15 0.98 .22 1.10 . 
1.71 .34 1.92 .48 2.82 .54 1-83 .35 1.99 .24 



3:30 
Mis. P.E. 



5:30 
Mis. P.E. 



7:80 9:30 I 11:30 

Mis. P.E. Mis. P.E. Mis. P.E. 



1.21 .33 1.21 .231.2,2, .31 
2.72 .36 Z.0Z .50,2.94 .52 



1. Horizontal rows. 



2. Vertical rows. 



This test served to confirm the other to a considerable degree, 
doubtless due to the chief common elements — motor control and keen- 
ness, with quickness of sight. The main divergence is at the second 
period, which the results make the best of the day. It is seen that 
the diurnal curve is the same for both horizontal and vertical rows, 
and this helps to confirm periodic differences which the large P.E.'s 
made doubtful, though these are mainly due to uncorrected practise 
effect and shortness of the series. The curve of these figures, if 
plotted, closely resembles that of the writer's diurnal efficiency as 
subjectively estimated. 

The diurnal course of speed of tapping seems from these results 
to differ markedly from the course of accuracy of movement. Both 
are alike in showing a low state of efficiency in the first hours after 
rising, but after that their curves are nearly inverse to each other. 
Pure accuracy appears to reach a maximum in the later morning 
hours, while tapping, in my own case at least, is at its best in the 
evening, when accuracy is about at its worst. Tapping also gives a 
different diurnal curve from other tests of speed, such as striking 
squares or writing numerals. In explanation of this difference, it 
is suggested that rapidity of tapping, as it requires a minimum of 
control but a maximum of neural excitement, may be expressive 
largely of 'nervousness.' If a person is most nervous in the evening 
— and this agrees with my own introspection — he would accordingly 



24 



DIURNAL COURSE OF EFFICIENCY 



be quickest in tapping at that time, but not most accurate in motor 
control. 

b. Normal Muscular Power. (a) Small and Large Muscular 
Groups. Since many of the conclusions as to muscular power and 
fatigue are based on work with small sets of muscles, it is a question 
of importance whether their efficiency at any time is a trustworthy 
symptom of the general muscular power. This will be discussed 
incidentally. 

First, the Cattell 1903 type of spring ergometer was used by 
subject I. to register 50 contractions of the thumb and forefinger of 
each hand, at every period, for 15 days; subject A made 40 con- 
tractions at each period for 14 days. However, the first 4 days, in 
both cases, were omitted for. practise. The figures in the table show 
the average number of kilos for 25 and 40 contractions, for the 
respective subjects, and the P.E.'s. 

Table VIII. 



Subject. 


No. of Con- 
tractions. 


8—9 A.M. 


3:30 to 4:30 P.M. 


10:30 to 11:30 P.M. 


Right. P.E. 


Left. P.E. 


Eight. P.E. 


Left. P.E. 


Right. P.E. 


Left. P.E. 


I. 1st 25.. 
2d 25... 

Average... 


300 
300 

300 


143 1.0 

107 0.9 

125 1.0 


115 0.8 
92 0.9 

103 0.9 


149 1.0 
111 0.8 

130 0.9 


115 0.6 

96 0.7 

105 0.7 


142 0.9 
109 1.1 

125 1.0 


109 0.8 

88 0.9 

98 0.9 


A— @40.. 


400 


126 1.9 


115 2.2 


137 1.7 


125 1.9 


124 2.3 


119 2.2 



With subject I. the record was kept for each half of the 50 con- 
tractions. The table shows some fluctuations, but on the whole both 
subjects show most strength in the middle period, as will be found 
to be generally true for strength. 1 

Lombard, 2 working with the Mosso ergograph as modified by 
himself, found the maximum power of the flexor muscles of the 
second finger to be reached at 10 a.m. and 10 p.m. (the higher maxi- 
mum) daily, and the minimum at 4 a.m. and 4 p.m. (the lower mini- 
mum). He assigns the diurnal rhythm of atmospheric pressure as 
the cause of these changes in motor power. In the same article it is 

X A cruder form of test was used by I., involving the hold-and-let-go method 
already mentioned. A lead ball, weighing 90 cm., was snapped, or ' plumped ' 
marble fashion, as far as possible on a soft board, marked off in centimeters. 
It registered its own distance each time by spots, which were erased after every 
10 snaps (the number taken with both hands at 7 A.m., 12 m., 5 and 10 P.M, 
for 12 days). The results, in average cm. distances, were as follows: for the 
right hand, 54, 56, 57, 54; and for the left, 50, 55, 56, 53. Only the greatest- 
least differences here are of consequence, though the order seems without doubt 
a real one with me. 

2 ' Some Influences Affecting the Power of Voluntary Muscular Contrac- 
tions,' Jour, of Physiol., 13. 1892. 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 



'J.O 



found that, among various influences increasing the power, food and 
sleep are very important. "With this true his morning maximum 
should be much in excess of the night one, but, as a matter of fact, it 
is less. It is also hard to see how the slight barometric change 
occurring at Worcester, where the experiments were made, could be 
so decidedly influential. Lombard 1 also found the diurnal variations 
in height of knee-jerk to be directly related to the barometric pres- 
sure and inversely to the temperature, but mainly dependent on 
hunger and fatigue, which are highly depressive (p. 67). Here the 
order was a morning maximum and a minimum at night, the decline 
being irregular; in general the knee-jerk was larger after each 
meal (p. 68). 

Patrizi, 2 using the Mosso machine in experiments on himself and 
another adult male in early morning, early afternoon, evening and 
midnight, discovered the 2 :30 p.m. period to be the best ; the evening 
was better than the morning, and the midnight result was about 
equal to that of the morning — an order but slightly different from 
that of my own results. He also quotes Buch as having found (with 
the dynamometer) a low muscular power in the morning; greater 
after luncheon, and greatest after dinner. 

Harley, 3 also making use of the Mosso ergograph, in experiments 
on himself, found the diurnal variations under ordinary conditions 
to be : maximum about 3 p.m. and minimum at 9 a.m. (his experi- 
mental day was only from 9 a.m. to 8 p.m.), as shown by Table IX., 
in kilogram-meters. 

Table IX. Variations in Normal Musculab Poweb — Ebgogbaph (afteb 

Harley). 

Hour 9 10 11 12 12345678 

Work 6.2 6.4 8.7 7.0 9.5 8.2 9.9 7.8 8.9 8.7 7.2 8.8 

The agreement of this result with what has preceded is obvious. 

Christopher 4 employed the ergograph for tests 90 seconds long 
every hour from 8 :30 a.m. to 3 :30 p.m., one day, on 1,127 schoolboys 
and girls. More intensive tests were made on four children of 
each sex. He concludes that 

1 ' Variations of Knee-jerk, etc.,' Am. Jour, of Psych., 1: 5-71. 1887. 

2 J. Joteyko, ' Rev. Gengrale sur la Fatigue Musculaire,' L'Annee Psych., 
5: 1-54. 1898. 

3 ' Effect of Sugar and Smoking on Muscular Work,' Jour, of Physiol., 17. 
1894. 

4 ' Report on Child-study Investigation,' An. Rept. of Bd. of Ed. of Chicago. 
18G8-1S99. 



26 



DIURNAL COURSE OF EFFICIENCY 



1. The extremes of endurance and fatigue are greater in the 
morning than in the afternoon. 

2. Strength is not as great in the afternoon, but is better sus- 
tained than in the morning. 

3. In children the intellectual capacity varies as the physical 
condition. 

Smedley 1 repeated the experiments on six boys and six girls of 
another school and practically confirmed the other work, as reference 
to Fig. 3 will indicate. 



/•"i'ft.UT. "" £Jrt>oor<x-y\\'tcTg.StS. — CWica.90 ScUool; 
How of tKe TS<x\$. — 




Solid, line. = a-venvoe. record of Jill f>u.^'ih »j Qlcott Sckool. 

Broken. « = ff 

~Ji o-ct e. <L " = » « « » /2 " "7e*nyst*. « . 
Firs-c -CM o--f*ar CktV stoJ-V.fr— V-o.it, a.^~tty Sv^tiXty, 



These results suggest that fatigue may be a more influential factor 
with children than with adults and may modify the diurnal curve 
accordingly. This whole matter will be treated at length later. 

Oseretzkowsky and Kraepelin, 2 using Mosso's type of ergograph, 
found that the average height of contraction (measuring the amount 
of performance) was greater at 2 p.m.: but the number of contrac- 
tions (measuring the endurance) at 10 a.m. These experiments, 
being made only at the hours named, contribute only confirmatory 
evidence to what has already been produced. 

Storey 3 reports work, with a modification of this type of machine, 
on students of Stanford University, number not given. The first 

1 ' Report on Child-Study Investigation,' An. Rcpt. of Bd. of Ed. of Chicago. 
1899-1900. 

2 ' Ueber die Beeinflussung der Muskelleistung durch verschiedene Arbeits- 
bedingungen,' Psych. Arbeiten, 3: 643 seq. 1901. 

3 Some Daily Variations in Height, Weight and Strength,' Am. Phys. Ed. 
Rev., 6. 1901. 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 



27 



series was from 8 a.m. to 6 p.m. and shows the maximum at 4 p.m. 
and minimum at noon — but slightly below the 8 a.m. figure. In a 
second series — details lacking — from 7 a.m. till 11 p.m., the highest 
point occurred at 9 p.m. and lowest at 7 a.m. 

Subsequently, 1 for himself, he found that "there is a normal 
decrease in ability to do muscular work between 2 and 5 p.m." 
(p. 193). This must be a misprint, for at another place he says 
"the morning max. comes at or near 10 a.m and the afternoon max. 
at or near 4 p.m.," and this is borne out by his tables, which are, 
however, not always clear. 

Very recently 2 he has made an extended study of the matter 
which, on the whole, confirms his earlier results and conclusions. 
Half the article describes the rather complex apparatus used — his 
own modification of the Lombard ergograph, employing weight or 
spring resistance, as desired. His method of exhibiting results is 
open to criticism, for only the roughest comparison of groups is 
possible, and that not of the best sort. How much was gained or 
lost is usually the most essential thing to know. The results show 
the number of times that gains or losses in power were found for 
the successive hours, when each was compared with the preceding. 
The unequal numbers of trials at the different periods show that the 
false assumption was entertained — alluded to before 3 as made by 
many authors— that incomplete records of some of the days repre- 
sented give reliable data for such relational procedure as the prob- 
lem involves. Storey himself, a well-trained subject, comes first 
in the table. A language student, 21 years old, taking no regular 
exercise, gave the results in the second division of the table. A law 
student and athlete, 21 years old, is reported in the third section, 
while three adult mechanics gave the results of the last section. 



Table X. Comparison 


OF 


Hourly Ergographic Records- 


—After 


Storey. 


No. of 

Subjects. 




6-7 


7-8 


8-9 


9-10 


10-11 


11-12 12-1 


1-2 2-3 


3-4 


4-5 


5-6 


6-7 


7-8 


8-9 


9-10 


1 


Gaining. 




6 


24 


16 


12 


4 


5 


11 28 


14 


2 


3 


5 


3 







Losing. 







1 


5 


4 


20 


1 


3| 1 


6 


16 


17 


1 


3 


5 




1 


Gaining. 


6 


6 










9 










5 


5 


2 


1 


Losing. 


2 


1 













1 








3 


5 


8 


4 


1 


Gaining. 








11 




8 




5 ! 


12 




10 










Losing. 








1 




6 




10 ' 


3 
3 




4 










3 


% of gains. 




61 




52 


21 ; 




% of losses. 














33 






6 




15 




48 



1 ' Daily Variation in the Power of Voluntary Muscular Contraction,' Am. 
Phys. Ed. Rev., 7. 1902. 

2 Studies in Voluntary Muscular Contraction, Stanford Press, pp. 60. 
1904. 

3 See above, p. 2. 



28 DIURNAL COURSE OF EFFICIENCY 

With the Upham dynamometer Storey then tested, in all, several 
hundred Stanford students by one grip before and one after an 
hour's gymnasium practise in classes at 10-11 a.m. (1,653 records 
for each hand) ; 11-12 a.m. (1,772) ; 3-4 p.m. (1,366) ; 4-5 p.m. 
(1,990) ; 5-6 p.m. (2,726). His main object was to ascertain the 
influence of gymnasium work on motor power, but, considering this 
work a constant factor, the above periods can be compared. The 
results are thus stated: "there is evidence of a morning period of 
muscular ability between 10 and 11 a.m. ; a subsequent diminution 
between 11 and 12 ; a tendency to rise between 3 and 4 p.m. ; about 
the same condition between 4 and 5 ; and finally there is evidence of 
a tendency to lose power between 5 and 6 p.m." (p. 49). 

This, he truly says, verifies all the preceding work. He fails to 
call attention to the early morning degree of inefficiency, though its 
presence is indicated by the high gains at the 8-9 and 9-10 periods. 
These results being in such a form as to give no definite idea of the 
real quantitative difference of efficiency at the different hours can 
not be closely compared with the work of other authors, but the 
divergence between his results and mine lies almost wholly in the 
extent of the noon and night drops. As to the general form of the 
diurnal curve, they are alike. 

The present writer also tested the strength of the grip, first using 
Collin's oval dynamometer. This instrument was also used in a set 
of leg-back tests, to be treated very soon. For convenience both 
results are incorporated in Table XI. 

These figures point rather consistently one way, being similar to 
Storey's save in the particulars mentioned above. 

My own individual order, of an early minimum and late after- 
noon maximum, is placed beyond all doubt by three other series. 
The first was for 30 days in autumn, under great regularity of 
external and subjective conditions. Five grips at each of 7 periods 
were taken. The second was also for 30 days, morning and night, 
2 grips at each. The third was for 12 days, 11 periods and 2 grips 
at each. The last two were taken with the Narragansett dynamom- 
eter, registering higher than the Collin 's instrument, which was used 
in the first series. The great amount of material secured enabled 
me, however, to transmute the results of the one into the unit of the 
others with but slight absolute error, that would not at all affect 
the relative standing of the periods. To eliminate practise effect, 
the first ten days' records of the first two series are omitted; no 
allowance was made in the third, which immediately succeeded the 
second in point of time but stands second in the table. 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 29 

Table XII. Musculae Power — Hand Dynamometer. 



Subject I. 


No. of 


7:00 A.M. 


8 : 30 A.M. 


10:00 A.M. 


11:30 A.M. 


1-1 : 30 P.M. 


3:00 P.M. 


Grips. 


Kilos P.E. 


Kilos P.E. 


Kilos P.E. 


Kilos P.E. 


Kilos P.E. 


Kilos P.E. 


r 


100 


60.7 0.17 




63.5 0.16 




64.9 0.18 




Eight. .J 


24 
40 


60.8 0.27 
60.2 0.23 


6.30 0.26 


65.2 0.23 


66.2 0.22 


66.1 0.32 


66.2 0.28 


r 


100 


56.6 0.18 




59.3 0.18 




60.7 0.18 




Left , j 


24 
40 


52.2 0.36 
54.1 0.19 


54.1 0.30 


56.0 0.33 


58.2 0.28 


58.3 0.37 


58.1 0.32 


Subject I. 


No. of 


4-4 : 30 P.M. 


6:00 P.M. 


7-7 : 30 P.M. 


9:00 P.M. 


10-10:30P.M. 


11-12:00P.M. 


Grips. 


Kilos P.E. 


Kilos P.E. 


Kilos P.E. 


Kilos P.E. 


Kilos P.E. 


Kilos P.E. 


f 


100 


66.2 0.19 




63.7 0.18 




61.7 0.17 


60.7 0.21 


Right. J 


24 
40 


67.3 0.25 


69.0 0.30 


67.1 0.22 


66.0 0.23 


64.2 0.25 


63.9 0.33 


f 


100 


61.7 0.20 




59.5 0.17 




58.0 0.17 


56.6 0.22 


Left j 


24 

40 


59.2 0.24 


60.1 0.22 


58.0 0.35 


56.3 0.31 


54.1 0.31 


57.7 0.19 



Attention is here called to Table V., showing various groups of 
males and females tested as to forearm strength. It will be noted 
that the men did almost uniformly better in the afternoon than in 
the morning, while the females were about evenly divided. How 
these results are to be construed has already been mentioned and 
needs no fuller comment at this point. 

The larger muscular groups are not so readily tested. At an 
international meeting of the University Physical Directors at Prince- 
ton, in December of 1903, an attempt at agreeing on the best gym- 
nasium methods of testing general muscular efficiency was unsuc- 
cessful, and it was decided to temporarily continue the old ones with 
certain modifications. This suggests the difficulty of getting ade- 
quate tests. 

Floor Dip. This was meant to test the arm muscles mainly, 
and consisted in extending the (rigid) body parallel with the floor, 
on toes and hands, and then alternately raising and lowering it by 
the arms as rapidly and as often as possible, efficiency being measured 
by the number of times it was thus completely raised. The tests 
were on myself for twelve days, but the first three were omitted and a 
small correction made on the rest for practise. The results are 
decisive for the periods shown. 

7 a.m., 17.2 (P.E., .15) ; 12 m., 21.3 (.34) ; 

5 p.m., 22.6 (.28) ; 10 p.m., 19.3 (.15). 

Floor Squat: a test for leg muscles in which the subject alter- 
nately squatted and raised himself 100 times as rapidly as possible. 
An extended effort to measure the deficiency present by the shorten- 
ing of the time the subject could hold his breath after the exercise, 
3 



30 



DIURNAL COURSE OF EFFICIENCY 





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COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 31 

or by the increase in pulse rate, proved fruitless. Then forty-pound 
dumb-bells were held in the hands and quick fatigue secured by 
squatting as before, in a short series. The results were too meager 
for quantitative expression but quite similar in tendency to those 
of the floor dip for arm muscles. 

Hand-foot Dynamometer: designed to test combined arm, back 
and leg strength. It is made up of the Collins oval dynamometer, 
having a kilo scale for use when the instrument is pulled endwise 
and equipped with the necessary handle and foot attachments for 
pulling. A short length to the whole, 14 inches, insured full use 
of the leg muscles as the subject sat on the floor and pulled. The 
operations were : right hand and foot, left hand and foot, and finally 
both hands and feet, three times each period. The results are shown 
in Table XL, while Table V. gives some results for two Filipino 
groups, with whom Tiemann 's pulling apparatus was used, also regis- 
tering in kilos. There is no radical discrepancy between these and 
preceding results. Though the P.E. is sometimes large, it is clear 
from the whole course of the figures that the middle of the day, in- 
cluding the afternoon, is a time of greater muscular strength than 
either morning or evening. 

The curve of strength efficiency seems, therefore, well established 
for the following course, and this probability will be strongly rein- 
forced below by further data : a beginning minimum in early morn- 
ing, a fairly rapid rise till 11, a level or slight decline till 1 p.m. 
(± 1 hour), an increase to the maximum at 5 (±1 hour), thence 
a fall till bedtime. Explanation of this is attempted in Part D. 

( o ) Comparative Functioning of Muscle Groups. As to whether 
the work of very small groups can be taken as indicative of the gen- 
eral muscular condition, an assumption long and often made with 
little attempt at proof, it appears from the above tables that the 
assumption is in reality well founded. In order to avert confusion, 
attention was not called to this point in passing, nor to the one suc- 
ceeding, and their verification must, therefore, be retrospective on 
the part of the reader. 

(c) Bilateral Symmetry. Regarding this matter, a review of 
Tables V., VI., VIII., XI. and XII. will disclose the fact that, 
although fluctuations occur, yet as a whole the figures show the same 
general course of efficiency for both sides of the body. The other 
evidence obtained agrees on this point. Lombard 1 with the ergo- 
graph noted that the strength may be greater on one side when 
least on the other, but that 'the major variations occur simultane- 

1 ' Fatiguing Voluntary Work,' Jour, of Physiol., 14. 1893. 



32 DIURNAL COURSE OF EFFICIENCY 

ously on the two sides' (p. 114), and Storey, in a work already 
cited, with many subjects found the same. 

c. General Motor Control. Experiments with the ataxiagraph 
to determine relative steadiness in standing for different times of 
day, and with the automatograph to determine changes in involun- 
tary movement, were planned but could not be carried out for lack 
of time, though the author is convinced by rough, tentative tests in 
balancing, etc., that the field is fruitful for this problem and would 
throw light on the other results. 

d. Complex Motor Activity. Of course there is no jump be- 
tween the following and what has preceded. Attempt was made to 
get data on activities of a more comprehensive character, first by 
means of a questionnaire designed particularly for physical directors 
and athletes, and containing questions as to what their experience 
would lead them to say on the matter of recurrent periods of varying 
ability, and their objective grounds for the opinion. The few replies 
that have been received are suggestive. 

Mr. J. G. Lathrop, Physical Director 1 of Schools at Southboro, 
Mass., says: "I have never considered it possible for me or any one 
under me to do as good performances in the morning as in the 
afternoon and that, so far as I know, is the experience of others. 
This, I consider, applies to any form of athletic work." 

Dr. G. L. Meylan, Medical Director of Columbia Gymnasium, 
after long experience as physical director, corroborates these words 
of Mr. Lathrop. Mr. Davis, his assistant, holds the same decided 
opinion, and both describe various performances in substantiation 
thereof. 

Miss Louisa Smith, Director of the Bryn Mawr Gymnasium, re- 
plied thus : ' ' We have athletics only in the afternoon and no compari- 
sons can be made. But I have noticed this : when we used to have both 
afternoon and evening classes, the students of the afternoon classes 
did the better work in educational gymnastics. In our physical 
examinations, too, I have noticed that those strength tests that are 
taken in the early part of the day average better than those taken 
between 9 and 10 in the evening." Here we find the same as set 
forth above for females. 

Mr. C. H. Robinson, Harvard athlete, 21 years old, submits this : 
"Last winter [1903] I competed in the shot-put at the Boston 
Athletic Association games and the best distance I could get was 
40 feet. These games came Saturday night. On the Monday fol- 
lowing I returned to my practise in the afternoon and easily reached 

1 Now track-team coach at Harvard University. 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 33 

44 feet. I have found this same fact true when I worked in the 
morning." He thinks the time of the maximum is determined by 
that of practise — which is only partly true. 

Mr. T. G. Meier, another Harvard athlete, 23 years old, says 
that he "has never noticed any particular difference between morn- 
ing, afternoon and night scores ' ' ; but mentally the morning seems 
best, with periods of lesser alertness after lunch and dinner, and 
then an efficient one from 8 p.m. to 12 m. This case must be noted 
as an apparent exception. 

Under the present heading will also be discussed certain observa- 
tions of manual labor in factories, made by the author at various 
times through several months. The main results are given in Table 
XIII., which reveals also the chief conditions. But some words must 
be added in fuller description of each group. 

The first group 1 is the most noteworthy, by reason of the regu- 
larity of the work, the basis of pay, and the number of hours per day. 
Its members were all experienced stitchers except the last, in whose 
case a correction was necessary for practise effect. They worked at 
top speed, presumably, as long as the material was supplied by the 
'gathering machines', which was about 45 or 50 minutes out of each 
hour. That is, all were obliged to stop these few minutes while the 
supply 'piled up' for the succeeding hour's run. At 12, 5 and 9 p.m. 
they worked only half an hour. Other than this the individual stops 
were insignificant. One was sick four days, another transferred to 
other work for a day, etc., so that although observations were con- 
tinued eleven days no one is reported for the full time. The first 
day's work was disregarded entirely, as it was found to be much 
affected by the initial experience of being observed. The same was 
true with the second group. Ordinarily, 120 magazines at a time 
were given to each worker, while, on my part, the time required to 
do this number, or any multiple of it, was taken just as often as it 
could be caught exactly, and subsequently reduced to the form shown 
in the table. 

In the second group the first two girls were experienced and 
piece-workers; the rest were inexperienced and worked partly by 
piece and partly by time, hence it was useless to attach P.E.'s to 
their averages. When paid by the thousand, they did from 30 to 
60 per cent, more than when paid by the day. Through the kind- 
ness of the foreman 2 the work was given to them in even hundreds ; 
otherwise it would have been impossible to get correct records of 

1 The work was the binding of a 900,000 edition of Everybody's Magazine 
by the Trow Directory Co., New York City. 

2 These observations were made at Dennison and Sons, New York City. 



34 



DIURNAL COURSE OF EFFICIENCY 



more than two girls at a time. In fact, several days were devoted to 
the first two before the above arrangement was instituted, and tab 
was kept of the individual holders made. After that the time per 
100, for each of the eight, was taken as frequently as it could be 
caught, together with the corresponding time of day. More labor 
than for the first group was required to reduce these data to a uni- 
form basis. The ten-minute basis was chosen to agree with the first 
group, where it had been selected to avoid the use of four-place 
numbers for the hour. During most of the time the work was dis- 
tributed to the workers by the author, which insured better control 
of the conditions. 

The third group covers cases where reliable records for only one 
or two days were secured. 1 In the pursuit of this phase of the 
general problem much valuable time was wasted in seeking oppor- 
tunity for suitable observational work, 2 but the trouble did not end 
there. Some people naturally object to being watched so closely 
and especially when on time-work. This would not be in evidence 
till after the first day. In several instances records were thrown 
away for wilful 'soldiering'. To make these results from various 
sorts of work comparable it was necessary to treat them as indicated 
in the table. That is, -f- 11 for the first subject means that she was, 
between 8 and 9 a.m., 11 per cent, above her average efficiency for 
the whole time observed. 

Table XIII. Female Industrial Labor. 

I. Magazine Wire-stitching. — Average Number Done per Each 10 Minutes 
of the Hour. — Piece-rate Basis of Pay. 











8-9 


A.M. 


9-10 


10 


-ll 


ll 


-12 


12-1 


(12:30) 


Subj. 


Age. 


Days. 


Nights. 






























No. 


P. E. 


No. 


P. E. 


No. 


P. E. 


No. 


P. E. 


No. 


P. E. 


1. 


27 


9 


4 


148 


1.38 


156 


1.09 


158 


0.47 


155 


1.39 


157 


1.06 


2. 


24 


9 


3 


144 


1.42 


156 


1.54 


155 


2.71 


155 


2.32 


152 


1.79 


3. 


20 


10 


5 


146 


1.81 


153 


1.43 


153 


0.88 


150 


1.26 


158 


1.23 


4. 


32 


10 


3 


138 


1.03 


149 


0.79 


150 


1.04 


156 


1.11 


156 


1.51 


5. 


20 


9 


3 


128 


2.62 


140 


2.33 


142 


2.02 


141 


2.32 


149 


1.43 


6. 


26 


10 


4 


109 


0.85 


110 


0.71 


108 


1.14 


109 


0.82 


110 


1.05 


7. 


23 


5 


3 


110 


1.24 


115 


1.59 


119 


2.48 


111 


2.28 


118 


2.34 


8. 


19 


7 


3 


111 


1.67 


114 


1.94 


118 


2.02 


117 


2.41 


115 


2.79 


At. 


24 


8.6 


3.5 


129 


1.59 


137 


1.43 


138 


1.59 


137 


1.74 


139 


1.65 



i For these records I am mainly indebted to J. English and Sons and 
Dennison and Sons, New York City. 

2 What obstacles one encounters on this score is suggested in the following: 
5 each of apparently the best representatives of 20 lines of manufacture were 
selected and a carefully written letter sent to each, stating aims and needs, 
together with stamped addressed return envelope. Of these 100 letters, 6 were 
returned unopened, 7 unfavorably answered, 9 favorably answered, and 78 
ignored entirely. Of the 9, 5 factories were distant from New York, 3 were 
unfit for the work, and 2 were used. 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 



35 











1-2 P.M. 


2 


-3 


3-4 


4-5 


5-6 (5:30) 


Subj. 


Age. 


Days. 


Nights. 




























No. 


P. E. 


No. 


P. E. 


No. 


P. E. 


No. 


P. E. 


No. P. E. 


1. 


27 


9 


4 


156 


0.90 


158 


1.42 


152 


0.81 


153 


1.64 


154 1.71 


2. 


24 


9 


3 


157 


2.62 


162 


1.23 


158 


2.90 


162 


2.91 


154 1.79 


3. 


20 


10 


5 


156 


1.02 


156 


1.53 


151 


1.56 


153 


1.51 


156 1.11 


4. 


32 


10 


3 


155 


1.19 


151 


1.01 


147 


1.07 


152 


1.00 


151 0.97 


5. 


20 


9 


3 


143 


2.40 


144 


2.21 


143 


1.87 


143 


2.43 


147 2.60 


6. 


26 


10 


4 


113 


0.97 


113 


0.85 


113 


0.62 


108 


0.78 


106 1.07 


7. 


23 


5 


3 


126 


1.24 


125 


2.27 


121 


2.49 


114 


3.23 


112 3.42 


8. 


19 


7 


3 


111 


1.57 


112 


1.66 


112 


1.82 


112 


2.28 


105 1.77 


Av. 


24 


8.6 


3.5 


140 


1.49 


140 


1.52 


137 


1.64 


137 


1.97 


136 1.80 



Siily. 


Age. 


Days. 


Nights. 


( 

No. 


>-7 
P. E. 


No. 


r-8 

P. E. 


t 
No. 


-9 
P. E. 


9-10 (9:30) 
No. P. E. 




1. 


27 


9 


4 


157 


1.12 


158 


1.01 


163 


0.93 


164 


1.28 




2. 


24 


9 


3 


163 


2.86 


160 


0.62 


158 


0.00 


159 


62 




3. 


20 


10 


5 


156 


1.58 


156 


1.72 


157 


1.31 


157 


1.63 




4. 


32 


10 


3 


160 


3.82 


155 


2.41 


152 


1.12 


162 


3.75 




5. 


20 


9 


3 


148 


3.48 


148 


2.29 


142 


2.61 


140 


3.56 




6. 


26 


10 


4 


117 


2.06 


116 


2.00 


116 


1.60 


121 


1.92 




7. 


23 


5 


3 


121 


2.51 


115 


2.39 


115 


2.35 


111 


2.43 




8. 


19 

24 


7 


3 


110 


1.78 


118 


1.39 


114 


2.83 


113 


2.71 




Av. 


8.6 


3.5 


141 


2.40 


141 


1.73 


140 


1.60 


141 


2.24 





II. Making Paper Coin-cases. — Average Number Done per Each 
10 Minutes of the Hour. 



Subj. 



Age. 



18 
16 
16 
17 
16 
16 
15 
14 



Days. 



10 
9 
6 
5 
4 
3 
5 



Pay 
Basis. 



Piece 






8-9 A.M. 
No. P. E. 



94 
74 
47 
61 
49 
50 
52 
40 



1.66 
2.10 



9-10 
No. P. E. 



97 
79 
48 
61 
50 
41 
50 
43 



1.21 
1.14 



10-11 
No. P. E. 



94 
76 
46 
62 
48 
43 
49 
41 



1.29 
0.81 



11-12 
No. P. E. 



92 
72 
46 
58 
43 
45 
50 
39 



1.42 
0.56 



89 
71 
47 
61 
39 
45 
52 
36 



1.90 
1.99 



Av. 



16 



5.6 



58 



59 



57 



56 



55 



Subj. 


Age. 


Days. 


Pay 


1-2 P.M. 




2-3 


3-4 


4-5 


5-6 


(5:30) 










No. 


P. E. 


No. 


P. E. 


No. P. E. 


No. P. E. 


No. 


P. E. 


1. 


18 


10 


Piece 


97 


1.56 


97 


2.11 


94 1.98 


90 1.16 


87 


1.49 


2. 


16 


9 


u 


73 


1.73 


70 


1.34 


70 1.42 


73 1.55 


77 


1.64 


3. 


16 


6 


U3 


51 




50 




44 


43 


42 




4. 


17 


5 




59 




53 




51 


50 


52 




5. 


16 


4 


49 




47 




44 


43 


42 




6. 


16 


3 




48 




47 




46 


44 


34 




7. 


15 


5 


8B 


47 




44 




45 


45 


42 




8. 


14 


3 


Ph 


41 




40 




43 


36 


33 




Av. 


16 


5.6 




58 




56 




55 


53 


51 





36 



DIURNAL COURSE OF EFFICIENCY 



III. Numbering Checks and Ledger-lines. — Hourly Per Cents. Above 
or Below the Day's Average Rate. 



Subj. 


Age. 


Days. 


Nights. 


8-9 A. M. 
No. 


9-10 
No. 


10-11 
No. 


11-12 
No. 


1-2 P.M. 

No. 


2-3 

No. 


3-4 

No. 


4-5 
No. 


1. 
2. 
3. 
4. 
5. 
6. 


24 
19 
21 
32 
18 
36 


2 
1 
1 
1 
1 
2 


32 

"35 
S3 

eq 

a 

H 
Piece 


+ 11 

— 19 

+ 8 

— 4 

— 12 

— 6 


+ 9 
-10 
+ 10 

— 3 

+ 16 

— 


+ 4 

+ 6 
— 2 
+ 32 
+ 6 


— 7 
+ 14 
+ 6 
+ 4 
+ 31 
+ 3 


— 15 
+ 18 

— 12 
+ 6 
+ 9 




+ 1 
+ 9 

— 2 

— 3 
—18 




— 6 
+ 2 

— 12 
4- 3 

— 25 

— 3 


+ 3 

— 14 

— 4 

— 1 

— 32 




Av. 


25 


1.3 




— 3.7 


+ 3.7 


+ 7.7 


+ 8.7 


+ 1.3 


— 2.2 


— 6.8 


— 8.0 



In considering these figures, if one were to look only at the total 
averages, it would not be very troublesome perhaps to read off what 
they most probably meant. That would not exhaust the facts, 
however, and might be misleading. From this standpoint it might 
be said that the first group shows increasing efficiency till 3 p.m., 
then a decrease till 5 :30, then a marked recovery and maximum rate 
till 9 :30 ; in the case of the second, a morning maximum, followed 
by decrease till 12 :30, then a sharp recovery and a succeeding grad- 
ual descent ; and in the third, a gradual increase to a noon maximum, 
and then a more rapid decrease to an evening minimum. Of the 
individual curves of a group, a rather large proportion follows the 
respective group curve. Thus, 1, 2, 6, 7, in I. ; 1, 4, 5, 7, 8, in II. ; 
and 2, 5, 6, in III. This is more evident in the plotted curves, of 
which only those of the wire-stitchers were drawn. 



A..M 



/P,M 




IOO 



Fig. 4. Magazine Wire-stitching by Females — see Section 1 of Table XIII. 

What specifically need attention are the fluctuations occurring at 
the first, fifth, tenth and fourteenth periods. In the first, 17 sub- 
jects show low efficiency and only 5 show a relatively high one. 
This is further confirmation of what has already been found for this 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 37 

period. -A trained 'observer' for Gunn, Richards & Co., of New 
York City — their business is to introduce into factories new systems 
of shop management and production, and in the establishing of ' unit 
times' for the separate operations involved in the making of many 
different articles they have made thousands of observations 1 on 
the speed of work — says this morning inefficiency, also noted by him- 
self, is 'due to the absence of the foreman.' But in the present 
instances this condition never occurred and could not at all be the 
true reason. In addition, piece-workers would be supposed to have 
the same prime incentive to maximum activity present at this as at 
any other period of the day. 

At the 12 :30, 5 :30 and 9 :30 periods several factors figure very 
effectively. Here the most pronounced fatigue tends to be offset 
by what has been termed 'end-glow' — the strenuous attempt to in- 
crease the output to the utmost limit at the last moment. These 
features are so characteristic that no correct interpretation of the 
curves is possible without their consideration. The periods imme- 
diately succeeding those named are influenced not only by rest and 
food, but also by the social intercourse which has intervened since 
the last work period. Reference is again made to Part D, where 
general treatment of these factors is preferably taken up. 

With these things in mind, and due reference to age and pay- 
basis, some definite conclusions can be formulated from the indi- 
vidual records. 

First, piece-workers tend to follow the end-glow type and time- 
workers the fag-end type. In group I., of the 24 cases at the three 
periods mentioned, 15 show the typical trait, whence it is safe to 
judge that at least half the rest are affected by it, to a lesser degree. 
Of the 16 cases in group II., 7 are of this type and 6 of them were 
directly due to piece-work. 2 And even the exceptional case of sub- 
ject 1 is fully accounted for by the fact that she usually set 4,000 
as the limit for the day's work and was able to reach this without 
special effort, thus becoming really a time-worker. Of the 12 cases 
in group III., 5 follow the type in question, 1 of whom was a piece- 
worker. The influence of my presence would be more apparent in 
this group and would naturally be more pronounced at these than 
at other periods, since few can refrain from endeavor to 'put the 

1 The best stop-watch (also time-book) for all classes of observational 
work, of which the author is aware, is one designed for this purpose by S. E. 
Thompson, C.E., West Newton, Mass. 

2 It should be noted here that the period prior to each of the three in ques- 
tion may also be affected, because the arbitrary limitation of the periods allows 
only 25 or 30 minutes to each of these three. 



38 DIURNAL COURSE OF EFFICIENCY 

best foot forward' ; and in morning than in afternoon, of the one day. 
Personal knowledge of the workers suggests that at least five of the 
nine failures in the first group to follow the prevailing type were due 
to physical inability to maintain the requisite pace. Subject 7, who 
was sick four days, could not work up to 5 :30 and 9 :30 climaxes, after 
showing a decisive tendency to end-glow at the 12 :30 period. Sub- 
ject 8 was youngest and most inexperienced and on both accounts 
was unprepared to meet the physical strain necessary to make these 
special bursts of speed. For the same reasons, these two subjects 
fail to make a night gain where the other six do. As to the time- 
workers, the evidence seems as conclusive. The last six subjects of 
group II. were paid by the thousand for two days, and the records 
made then tend to overbear those of the other days. In but 1 of 
the 16 cases did there seem to be a naturally strong wind-up. The 
cases in group III. can not be said to alter these conclusions ma- 
terially, as they have not the same weight even if they evinced con- 
trary results. 

Second, it seems reasonable to believe that endurance as de- 
pendent on maturity is much involved. In fact, it is impossible to 
say how much the falling off in the production of the time-workers 
at the stated periods is to be accounted for on the ground of indul- 
gence of the feelings of fatigue, due to lack of the same incentive to 
high activity that piece-workers possess, and how much is to be al- 
lowed for the fact of physical inability due to immaturity and con- 
sequent real fatigue. To the author, the results for group I. seem 
due to the basis of pay in its stimulative aspect, while for group II. 
they seem considerably due to immaturity, save in the first two 
cases. It is not unworthy of note, in this connection, that of the 
five cases of this group mentioned above as showing high efficiency 
in the early part of the day, three are the youngest of the eight, all of 
whom have proportionately higher records at this time of day than 
do the adults. Their curve as a whole follows quite closely that 
found by Christopher for the Chicago school children, seen in Fig. 
2 above. 

Neither piece- nor time-workers can be thought to exhibit what 
would be the curve of earnest, ordinary work; but the former con- 
ceivably resemble the top extreme of such a group, where the maxi- 
mum product is reached, while the latter would represent the bottom 
extreme, where exists a minimum of accomplishment and a maxi- 
mum of yielding to the feelings of fatigue. It would scarcely be 
worth while to carry the analogy to the extent of determining the 
theoretical median or modal curve of such a group, to express its 
general tendency. Likewise, it is scarcely worth while to seek gen- 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 39 

eral 'type' curves of ability. That is, there is danger in the smooth- 
ing-out process which leaves to curves only their coarsest changes. 
It is the positive tendency of all present-day scientific methods of 
gathering, registering and measuring data to subdivide phenomena 
more and more in order to get a more accurate judgment of the 
whole fact in the light furnished by the more detailed and exact 
definitions of the separate parts. This is quite a contrary operation 
throughout to the process of smoothing. 

This danger can be thus illustrated: an increase of 20 per cent, 
in efficiency at a certain hour may be entirely due to a waking nap 
in the preceding hour, where a loss of only five per cent, was sus- 
tained by reason of the doziness. We should likely call the first men- 
tioned change worthy of notice and the other not, if smoothing were 
in mind, yet in reality the one could not occur without the other and 
indeed the results might, in its absence, be just the reverse. This is 
not purely hypothetical, since in my own case a partial loss of con- 
sciousness for five minutes in the afternoon frequently has a very 
appreciable mental effect for the better, though a long and real nap 
has the opposite effect. 

There is some satisfaction and there may be some practical ad- 
vantage in having such gross 'types' of endurance, etc., but they 
hold the same doubtful position as to actual explanatory desiderata 
that all other generalities occupy. It probably will be agreed that 
this table does emphasize the two types described, but it is easy to 
find deviations in the individual curves. Others than these two are 
hard to locate and depict. Kraepelin describes five or six fatigue 
'types', but is enabled to do so merely by grace of having used but 
four hours a day in his tests : the curves become more than propor- 
tionately complex when twice or thrice that length of time is utilized, 
and the number of individuals falling under each is correspondingly 
reduced. 

Attention has already been called to the early inefficiency in 
group I. ; it is now directed to the more notable fact that the highest 
point is reached at night by six out of the eight. That this would 
remain as the normal condition in regularly continued labor is not 
likely (each was allowed to work only every other night during the 
two weeks' continuance of the job). While the results will, there- 
fore, not permit the temporal fixing of maximum performance, they 
do serve to introduce a point of considerable practical and psycho- 
logical interest. That it was possible, after a full day of severe 
effort, to increase the output so notably and so long suggests how 
nicely the organism comes to be adjusted to the drains likely to be 



40 DIURNAL COURSE OF EFFICIENCY 

made upon it. It might be truer to say that there is in the early- 
part of a long day's work an organic or at least involuntary check- 
ing of the tendency to overdraw the store of available energy. Any- 
way, we seem never to reach the absolute maximum of exertion pos- 
sible to us. Not only end-glow, but a number of other things, espe- 
cially in the second group, caused marked increase of ability. It is 
worth knowing whether such induced bursts as the latter are clear 
gains or are counteracted by subsequent inefficiency. The solution 
of this question does not appear from our data, because of the many 
unexcluded factors. 

The wire-stitching done by the first group does not require any 
special accuracy of movement, but decidedly involves speed. Here, 
again, is suggested, as in connection with the tapping tests, the possi- 
bility of nervousness increasing the rapidity of certain sorts of 
movement that do not require precise muscular coordinations. 
Women presumably are more 'nervous' than men, and hence it be- 
comes inconceivable from the physiological standpoint that these 
could have worked all day near their speed limit and not have been 
neurally disorganized at the end. Their period of greatest speed 
of work thus coincided with their probable period of greatest 
nervousness. 

3. Brief Summary. — The necessity is shown of keeping separate 
the rate, accuracy and strength of movement and not lumping every- 
thing as merely 'physical ability', while the further division of the 
first two for different types of simple and complex movement is 
strongly suggested. Just what diurnal schedule each of these fol- 
lows has not been fully demonstrated, but some points have been 
definitely fixed. As to strength (not meaning endurance), there is 
ample reason for believing that most commonly the first morning 
power is relatively low, but subject to a fairly rapid rise till about 
11 a.m., when there is manifested a slight backward tendency till 
1 p.m. (± 1 hour), then a gradual ascent to the maximum between 
3 :30 and 5 :30, whence there is a much more gradual descent till 
bed-time, when a second minimal point is reached — with adult males. 
Females tend to push this curve back at every point, and children 
still farther, apparently due to their greater liability to physical 
exhaustion; men have more strength and are less likely to use it. 
As to rate and accuracy of movement, there is still found the defi- 
ciency at the extremes of the day, but with a marked tendency to 
more accuracy efficiency toward the morning end and rate efficiency 
toward the night end, and these tendencies are accentuated as the 
test for accuracy is more complex and that for rate more simple. 
Strength and speed may be increased by a highly nervous state, but 



COURSE OF PSYCHOPHYSIOLOGICAL EFFICIENCY 41 

accuracy is oppositely affected. Female shop operatives, in addi- 
tion to confirming some of the preceding points, tend as piece-workers 
to the end-glow type when approaching intermissions, and as time- 
workers and children to the opposite extreme, while both classes 
manifest ability to increase their product considerably, under special 
stimulation, at any portion of the day and despite the fact of pre- 
vious hard work. 



C. COURSE OF MENTAL EFFICIENCY 
I. The Simpler Mental Activities 

This field, having so much in common with the last, has its 
peculiarities, nevertheless, which serve to introduce the marked diffi- 
culties characterizing the study of psychic life. It was not because 
the ancients found the latter too easy a problem to be worthy of 
notice that scientific attention was turned outwards, but rather be- 
cause it was so fine-spun and intangible as to escape much notice. 
The 'popular mind' is yet quite free from introspective questionings, 
and any such ignorance of the presence of a problem is likely to be 
indicative of its difficulty. Aside from any spiritual considerations 
which might lead to the study of psychology as the science of the 
soul, there is every reason to believe that the mind's more imme- 
diately utilitarian use as a tool or means for meeting the various 
needs of the higher life in general — volitional, cognitive, esthetic, or 
whatever one may call them — will increasingly force itself to the 
front in one aspect or another. When it comes to determining the 
efficiency of this tool at different periods of the day, for the ends 
mentioned, the more radical complications of the problem emerge 
into view. It might be said that the last section had, on its mental 
side, most to do with volition; that the present would likely deal 
mostly with cognition; and the next, involving feelings of fatigue, 
etc., would touch upon emotion. With finer psychological analysis, 
it is seen that this program, even if fully realized experimentally, 
would still cover the field only in the grossest sense. 

1. Attention 

The tests of the fluctuation of attention, that Wiersma 1 first used 
and Pillsbury 2 repeated, seem rather tests of the senses employed 
than of attention itself. For instance, a certain weight was placed 
on a cork disk, of the same size, on the back of the hand, and the just 
perceptibly different weight was then determined, as also the one dis- 
tinguished with certainty. Between these two limits six weights of 
equal degrees of difference were used, the test of attention being the 
length of time that each of these could be distinguished from the 

1 ' Untersuchungen iiber die sogen. Aufmerksamkeitsschwankungen,' Zeit- 
schrift fur Psych, u. Physiol., pp. 179-198. 1902. 

2 ' Attention Waves and Fatigue.' Am. Jour, of Psych., 14: 314. 1903. 

42 



COURSE OF MENTAL EFFICIENCY 



43 



first as standard. For light and sound stimuli, six shades of gray 
and six gradations of sound were determined by the same principle 
as for pressure. Why it might not be a fatigue coefficient that is 
here obtained, where the senses are thus exercised, is not clear. 
Wiersma 's tests covered three days with each subject. Pillsbury 
used only the grays in his repetition of the experiment. Table XIV. 
gives the results of both authors. 

Table XIV. Attention — peb different senses — Wiebsma, Pillsbuby. 



Subject. 


Test. 


Morning. 


Noon. 


Afternoon. 


Night. 


Wiersma. 




Time. M.V. 


Time. M.V. 


Time. M.V. 


Time. M.V. 


H 


Pressure. 


204.6 10.9 






239.5 8.9 


161.9 14.1 


W 


«< 


201.0 6.1 






251.1 3.0 


283.5 1.7 


u 


Light. 


180.0 — 






228.4 — 


255.8 — 


<( 


Sound. 


217.2 — 






235.4 


256.1 — 


Male nurse. 


<< 


217.2 5.8 






209.2 6.2 


216.0 5.3 


Female nurse. 


<< 


241.6 1.7 






248.0 1.8 


242.0 4.6 


Female nurse. 


a 


202.2 4.8 






215.0 4.4 


197.0 3.6 


Pillsbury. 




No. VII Sum. 


No. 


VI I Sum. 


No. VII Sum. 


No. VII Sum. 


P 


Light. 


300 2.4 9.6 


245 


2.5 8.5 


337 2.6 8.2 


365 1.6 7.5 


H 


k 


287 3.4 9.4 


230 


2.6 8.7 


285 3.3 9.3 


300 2.9 9.0 


G 


it 


249 1.2 8.9 


181 


1.3 8.9 


265 1.2 8.4 


377 1.2 8.4 


W 


it 


275 1.5 5.4 


196 


1.6 6.3 





281 1.5 5.1 


F 


a 


73 5.0 18.9 


37 


4.7 18.2 


79 3.4 13.4 


63 4.5 18.8 


K 


a 


38 1.6 13.5 


42 


1.9 14.4 


41 3.4 14.6 


33 5.6 22.0 



No. = number of waves measured. 

V/I = ratio of visible to invisible periods. 

Sum = length of attention wave. 



Wiersma is uniformly worst in the morning and best at night, 
while H has another order. It is strangely concluded that those of 
little mental training do not show definite variations and that these 
are due to general practise in mental work. A tendency in students 
to raise the night-end of efficiency may exist, but his subjects are 
too few and incomparable, and the results too discordant, to allow 
such an inference. 

Pillsbury experimented on six subjects from one to six days. 
The first three records are obviously more reliable than the last 
three. With the exception of K (Kiilpe), who was a very strong 
night-worker, they point to a morning maximum and a night mini- 
mum in efficiency of attention. Pillsbury says that Slaughter and 
Bonser independently have found the attention wave to correspond 
to the Traube-Hering wave-length for blood pressure. This suggests 
a correlation with the diurnal variations in pulse and respiration 



44 



DIURNAL COURSE OF EFFICIENCY 



rates, which Galloway, in an unpublished investigation, finds really 
to exist. 

It is not easy to see how fatigue effects could fail to operate in 
such protracted experiments with senses where, according to the 
prevailing idea, it is wont to appear quite early. The main fact 
measured would then have been sensory more than attentional, as 
intimated above. The difference of opinion may be merely defini- 
tional. 

Lobsien 1 refers to some work by Schuyten, of Antwerp, on 
changes of attention in school children eight to ten years old, carried 
on for a school year — to determine atmospheric effect. At four 
periods of the day the number of times in five minutes they invol- 
untarily raised their eyes from an assigned reading was noted. The 
results having a bearing here may be briefly stated thus : ' ' The atten- 
tion of school children diminishes from 8 :30 to 11 and again from 
2 to 4; is greater at 2 p.m. than at 11 a.m., but always less than at 
8:30 a.m." Using the same method, Lobsien found the following 
results : 

Table XV. Variation of Attention of School Children — After Lobsien. 





Jan. 


Feb. 


Mar. 


Apr. 


May. 


June. 


July. 


Aug, 


Sept. 


Oct. 


Nov. 


Dec. 


A.M. 
P.M. 


64 
59 


59 
55 


57 
57 


55 
52 


47 
49 


45 

47 


39 

42 


— 


— 


52 
50 


55 
51 


62 
58 



Numbers mean per cents, of pupils not raising the eyes. 

It will be seen that the morning or afternoon is the better accord- 
ing to the time of year, morning being more favored on the whole. 
This method seems better than the preceding, is simple and easy of 
application and measurement. The results are more concordant, 
possibly due to age, as well as more reliable. 

2. Discrimination 

For testing discrimination of letters, I used, in most of the series, 
a printed form of 500 capital letters— 100 A's and 16 each of the 
other letters of the alphabet intermixed in irregular order. By some 
of the subjects, 1 of these 16 letters was marked out each period; 
by others, more than one. The marking out was done as rapidly as 
consistent with correctness and was timed by a stop-watch. The 
most conspicuous letters were not used, and the rest were so arranged 
that each occurred once in each period every three days, thus weight- 



1 ' Schwankungen der psychischen Kapazitat,' Pddag. Psych., V. Bd., 7 
Heft. 1902. 



COURSE OF MENTAL EFFICIENCY 



45 



ing each period alike as to the varying difficulty of different letters. 
The average time and its P.E., and the average number of omissions 
are shown for each subject in the following table : 

Table XVI. Discbimination of Lettebs — Letteb Blank. 



Subject. 


No. of 
Days. 


7-9 A.M. 
Time. P.E. Omis. 


12-2 P.M. 
Time. P.E. Omis. 


5-7 P.M. 
Time. P.E. Omis. 


9-11 P.M. 
Time. P.E. Omis. 


I. 1 letter 

II. " 
III. " 

V. 
VI. " 

Average 


14 
12 
12 
12 
11 

12 


58.5 0.76 1.2 
63.8 1.11 0.3 
42.0 0.69 0.6 
71.8 1.03 0.8 
42.5 0.43 2.3 

55.7 0.80 1.0 


54.8 0.69 1.3 
60.3 1.23 0.6 
41.0 0.74 0.7 
60.7 0.73 1.3 
41.3 0.70 3.0 

51.6 0.62 1.4 


54.8 0.57 2.3 

63.4 1.36 0.2 
44.0 0.53 0.7 
63.6 1.21 1.1 

40.5 0.70 2.5 

53.5 0.88 1.4 


59.0 0.62 1.4 

66.1 1.57 0.7 

44.5 0.61 0.9 

70.6 0.68 1.3 

40.2 0.70 2.2 

56.1 0.84 1.3 


( 1 letter 
T J 2 letters 

■.18 " 

14 << 

Average 


14 
10 
10 

8 

10 


58.5 0.76 1.2 

84.8 1.00 3.9 

112.2 1.19 5.1 

141.5 1.26 5.9 

99.2 1.05 4.0 


54.8 0.69 1.3 

76.3 0.91 4.2 
106.0 1.04 5.6 
131.6 1.99 6.4 

92.4 1.16 4.4 


54.8 0.57 2.3 

77.1 0.70 5.5 

108.1 1.91 5.6 

132.4 1.25 7.6 

• 93.1 1.11 5.2 


59.0 0.62 1.4 

81.6 1.36 4.2 

116.6 2.05 6.1 

140.0 1.63 7.1 

99.3 1.41 4.7 


,1 letter 
1 I 2 letters 
A ]3 " 

1 4 it 

Average 


14 

7 
6 
6 

8 


76.2 2.01 0.9 
97.0 0.88 7.3 

144.2 1.64 5.8 

167.3 2.13 6.9 

121.2 1.64 5.2 




79.5 1.61 0.9 

95.1 0.83 4.6 

139.3 2.05 8.0 

169.2 2.42 5.6 

120.8 1.73 4.9 


78.3 1.21 0.6 

107.8 0.93 3.9 

166.9 1.76 3.7 
182.1 3.12 6.7 

133.8 1.76 3.7 


IV. 2 letters 


10 


107.7 1.92 2.5 


103.0 0.96 2.8 


110.1 1.27 3.4 


118.6 1.32 2.9 



The maximum ability is found at noon, the minimum at the 
extreme periods. It being winter, the tests at the latter times were 
often performed under artificial light, which may account for some 
of the difference. The omissions seem to vary inversely as the time, 
which fact would also decrease the differences between periods, as 
to their total efficiency. Subject A does comparatively better in 
the morning and decidedly worst at night. 

Group B marked out two letters simultaneously and then a second 
combination of two on another blank, under a constant time-limit 
of 90 seconds for each period. The results appear in the next table, 
in terms of the average number of letters undone and omitted. 



Table XVII. Discbimination of Lettebs — Letteb Blank. 



Sub- 
ject. 


No. of 
Blanks. 


9 : 00 A.M. 
Undone. P.E. Omis. P.E. 


12 : 00 M. 
Undone. P.E. Omis. P.E. 


4 : 00 P.M. 
Undone. P.E. Omis. P.E. 


B 


32 


21.2 1.14 12.4 0.72 


26.1 0.98 11.1 0.97 


28.2 1.71 12.3 0.99 



This shows a gradual increase of inefficiency from 9 a.m. on. 
The difference here may be due to sex, as subject A also shows a 
much worse night rate in this than in most of her tests. This in- 
crease was in spite of practise effect. 
4 



46 



DIURNAL COURSE OF EFFICIENCY 



In a similar test, but using a book, subject I. marked out the e's 
on a page; then, in another series, the a's. The first period and the 
last two were subject to slight interruption, but the others to more. 

Table XVIII. Discrimination of Letters — Book Pages. 



,5 

02 


u 

1-1 


to ■ 


7:00 A.M. 
Time. P.E. Omis. 


10:00 
Time. P.E. Omis. 


12:00-1:00 P.M 
Time. P.E. Omis. 


4:00 
Time. P.E. Omis. 


I. 
I. 


e 
a 


12 
17 


27.5 .41 .73 

28.5 .32 .37 


26.2 .40 .99 
26.6 .29 .35 


27.2 .23 1.27 
27.1 .37 .41 


25.6 .19 1.01 

26.7 .34 .60 


Average 


15 


28.0 .36 .55 


26.4 .35 .67 


26.1 .30 .84 


26.2 .26 .80 



CO 


h4 


if 


7:00 P.M. 
Time. P.E. Omis. 


Time. 


10:00 
P.E. 


Omis. 


12:00 M. 
Time. P.E. Omis. 


I. 
I. 


e 
a 


12 
17 


26.0 .20 .74 
26.5 .35 .45 


28.7 
29.8 


.56 
.37 


1.12 
.21 


30.0 .23 .73 


Average 


15 


26.3 .28 .59 


29.2 


.46 


.66 


30.0 .23 .73 



No correction was made in 'time' for the varying number of e's 
to a page, as the same function is exercised in their absence as in 
their presence, but a slight allowance was made in ' omissions. ' The 
order of abilities is about that found by the previous test, and the 
inverse relation of rate and accuracy is again hinted at. 

Among the Exposition tests was one involving mainly judgments 
of shape and size, and a motor element. In a board, a foot square, 
were cut nine shallow holes of various sizes and shapes and in an 
irregular order. These shapes were partly in pairs, the members of 
which more or less closely resembled each other — in order to render 
their discrimination the more difficult. Blocks, shaped like the 
holes and supplied with handles, were to be inserted by the subject 
at the maximum speed possible and with the minimum error. The 
following average record was made by 60 Filipinos in the morning 
and 40 in the afternoon: a.m., time, 25.0 seconds, mistakes, 1.00; 
p.m., time, 25.5, and mistakes, 0.76. This is but a chance difference, 
if both ways of scoring be taken into account. 



3. Association 

Reaction-time, naming colors, and word associations will be con- 
sidered in this connection. All involve discriminative and motor 
elements in varying degrees. 

The experiments in reaction-time are limited in number. In 
simple reactions to a sound-stimulus, two subjects were tested with 
the Hipp chronoscope three times daily for four days, five reactions 
with each hand. In controlled reactions, two subjects were tested 



COURSE OF MENTAL EFFICIENCY 



47 



for seven days, reacting to colors exposed by an electrical drop- 
screen in about three-thousandths of a second. The combinations 
of colors in a first series of experiments were standard red and green, 
red and orange ; in a second series, red and the same red mixed with 
50 per cent, of orange (R-O), then red and red with 25 per cent, 
orange (O-R). 1 The results of both forms of tests are in Table XIX. 



Table XIX. Reaction-time and Time of Day. 



Subject. 


No. of 
Reactions. 


9 : 00 A.M. 


12 : 30 P.M. 


5 : 00 P.M. 


Time. P.E. 1 Time. P.E. 


Time. P.E. Time. P.E. 


Time. P.E. Time. P.E. 


Simple reaction. 


Eight. Left. Eight. Left. Eight. Left. 


I. 
VII. 


20 
20 


162 2.88 
142 3.87 


161 2.99 152 2.52 
133 2.74 132 3.21 


149 2.01 
118 3.32 


152 2.93 
129 3.16 


150 2.71 
124 3.37 


Controlled reactioi 


i. E. & G. E. & O. E. & G. E. & O. E. & G. E. & O. 


I. 
III. 


208 
208 


255 1.51 
247 1.51 


281 1.56 
272 1.27 


244 1.62 
246 1.16 


278 1.56 
264 1.46 


253 1.62 283 1.38 
244 1.11 268 1.38 


Controlled reaction 


. E.&E-O. E. & O-E. E. & E-O. E. & O-E. E. & E-O. E. & O-E. 


I. 156 
HI. 156 


265 1.45 
279 1.20 


274 1.26 
285 1.13 


265 1.39 
271 1.00 


276 1.52 
278 1.13 


266 1.39 
273 1.39 


280 1.26 

281 1.44 



The superiority of the later two periods is apparent, and it 
should additionally be said that on two of the days it was so cloudy 
(January) that electric lights had to be used a short part of the last 
period. Possibly the motor element here has much influence in 
shaping the curve. 

Ostanikow and Grau 2 measured four adults with the Hipp instru- 
ment—themselves, a servant (18 years) and a peasant (65). The 
periods were 9 a.m., 1, 4 and 7 p.m. They found the simple reaction- 
time shortest in early morning and the complex in early evening. 
Divergent results would be expected from so heterogeneous an age 
group. 

Work done by Cattell and by Ellis and Shipe in connection with 
fatigue investigations, will be referred to later (see p. 82). 

For the test in naming colors, ten one-cm. squares of each of ten 
different colors were pasted at intervals of one cm. on white card- 
board, in irregular order. The subjects named these aloud as rapidly 
as possible, taking the time with a stop-watch. By holding the card 

1 This is also part of an investigation by Dr. V. A. C. Henmon, Columbia 
University. 

2 Bechterevv, ' Ueber die Geschwindigkeitsveranderungen, etc.,' Neur. Central- 
blatt., 12, 9 Bd. 1893. 



48 



DIURNAL COURSE OF EFFICIENCY 



in different positions, the colors were presented in four different 
orders ; and the experiment was so arranged that the same order was 
not presented in any two consecutive tests, though each order was 
used during a whole series an equal number of times for each period 
of the day. In the results, the first two days' records were omitted 
in allowance for practise. 

Table XX. Naming 100 Colors. 



Subject. 




7-9 A M. 


12-2 P.M. 


4-6 P.M. 


9-11 P.M. 




Time. 


P. E. 


Time. 


P. E. 


Time. 


P. E. 


Time. 


P. E. 


I. 


1,000 


61.8 


0.76 


56.0 


0.62 


55.2 


0.48 


59.2 


0.51 


II. 


1,000 


68.8 


1.10 


62.1 


0.76 


63.1 


0.67 


67.3 


1.22 


V. 


1,000 


59.1 


1.30 


50.9 


0.74 


51.6 


0.73 


55.3 


0.44 


A 


1,000 


60.1 


0.91 


— 


— 


57.1 


0.97 


57.8 


1.15 



Here again the motor element may somewhat account for the 
obvious similarity to the diurnal curve already found for speed of 
movement. 

In a lengthy list of tests given to Columbia students in their 
entering and final years, this one shows in the results a decided im- 
provement to have occurred in the interval. This may be cor- 
related with the intellectual development which has presumably 
taken place, but may on the other hand be correlated with the phys- 
ical growth that has intervened. This test is not so simple as it 
seems. Among the perceptional, assoeiational, expressional and 
other factors, one can not say how the time should be distributed, 
and yet just such knowledge as this in all our tests is required to 
properly relate the results obtained. The progress made in this 
refined work of correlating different functions with reference to their 
common or dissimilar elements will largely determine the value of 
the experimental psychology of coming years, from both the scien- 
tific and the pedagogical points of view. 

In 'simple' word associations, at each period a list was used of 
16 words (4 nouns, 4 adjectives, 4 verbs, 4 adverbs and prepositions), 
selected at random but arranged in a definite order. After each 
word was to be written the first one occurring to the mind after 
seeing it. Time was taken as in the other tests. The lowest section 
of Table XXI. gives results. 

For controlled word associations, 420 words were selected, as 
nearly equal in difficulty as possible. From these, random lists of 
ten words each 1 were made up and these given to the subjects. It 
was hoped by a random arrangement to obviate differences of diffi- 

1 As ' supple, terse, aroused, insipid, ulterior, negligent, fitful, courage, pro- 
fuse, stately.' 



COURSE OF MENTAL EFFICIENCY 



49 



culty in the words. A word of opposite meaning was to be written 
after each one on the list. Words were chosen whose opposites could 
not be (easily) formed by annexation of prefixes or suffixes of nega- 
tion, or by omission of the same. Of course it was impossible to 
avoid this entirely, though the subjects were also instructed not to 
make use of such opposites. Those taking the test thus are reported 
in the first section of Table XXI. The middle section gives the 
resulting figures when A and I. used two of the lists at a period, the 
rate for each list being shown in the case of A. 



Table XXI. Wokd Associations — Simple and Controlled. 



Snbippt No. of 7-9 A.M. 12-2 P.M. 4-6 P.M. 9-11 P.M. 

■'■' ■'--'• Words. Time. P.E. Mis. Time. P.E. Mis. Time. P.E. Mis. Time. P.E. Mis. 



Controlled — 10 Opposites. 



I. 


100 


II. 


100 


III. 


100 


IV. 


100 


V. 


100 


verage 


100 


A. 


140 



69.7 2.72 

50.6 1.72 

48.4 1.27 

76.0 2.74 



0.5 
0.1 
0.1 
0.6 



54.2 2.23 1.9 



59.8 
63.8 



2.14 
3.01 



0.6 
0.1 



60.1 
43.6 
41.4 

74.8 



1.23 
1.71 

0.94 
2.83 



0.4 
0.1 
0.2 
1.1 



46.6 1.64 1.9 
53.5 1.67 0.7 



59.3 


2.46 


0.4 


46.0 


1.76 


0.0 


44.0 


1.36 


0.3 


70.7 


2.95 


0.8 


48.2 


1.19 


1.4 


53.6 


1.94 


0.6 


57.2 


2.07 


0.1 



70.3 2.32 0.3 

45.1 2.36 0.1 
45.0 1.68 0.1 

71.2 2.30 0.4 
45.0 0.96 0.5 



55.5 
61.2 



1.92 

2.86 



0.5 
0.2 



Controlled — 20 Opposites. 



I 


per 10 


100 


56.2 


2.12 


0.2 


55.8 


1.74 


0.6 


55.5 


1.97 


1.0 57.5 


1.86 


0.5 


A 


. 1st 10 


70 


46.0 


2.91 


0.2 








38.7 


1.91 


0.1 


47.7 


2.33 


0.1 


A 


. 2d 10 


70 


50.4 


3.00 


0.3 








39.4 


2.13 


0.1 


45.0 


2.97 


0.2 



Simple — 16 Words. 



I. 
A. 



160 
162 



51.8 
51.0 



0.51 
0.83 



51.4 0.58 



49.9 
53.8 



0.50 
0.92 



50.2 
53.9 



0.59 
1.10 



This table makes the first period of the day the worst, while noon 
seems the best. The P.E.'s show that a longer series is needed, but 
it would be exceedingly difficult to find in the 150,000 usable words 
of the English language 100 more with the requisite qualifications 
for this test. 

Fifty of these words were given to the group of young women, 
240 seconds being allowed in which to write the opposites. To bring 
this more into line with the others, the number of words undone was 
used as the basis of the estimates. The results were : 9 a.m., undone 
19.1 and mistakes 3.5 ; 12 m., 18.3 and 2.3 ; 4 p.m., 17.0 and 3.4. The 
differences here are not decisive: the P.E.'s are large, because the 
subjects hunted easy words instead of taking them seriatim. The 
morning figures are probably affected by newness of test. 

This test seems of doubtful utility for the present purpose, if it 
is admitted that writing ability varies for time of day. Subjects 



50 



DIURNAL COURSE OF EFFICIENCY 



I., IV., V., A and B took the rate test for writing and the general 
order of each in the two cases is notably similar (see Table IV., p. 
18). The quicker the real association-time of the individual, the 
greater would such vitiation be. Being designed for the use of stu- 
dents, the words picked were of two and three syllables, with some 
hard monosyllables needed to fill out the desired number. This 
meant long opposites, and much time devoted to the merely mechan- 
ical act of writing. Also, while 100 words at each period give fair 
chance for equal distribution of hard ones, the P.E. in this test will 
always remain large on account of them. The inverse relation of 
speed and mistakes, seen in the results, again shows the need of a 
coefficient which would allow the transmuting of the one into terms 
of the other, and it is not altogether improbable that such a figure 
could be found if careful search were made. 

4. Memory 

This was tested in several ways. Subject I. selected 1,200 Ger- 
man words, with which he was unfamiliar, and arranged them in 
random lists of ten each, with their corresponding English meanings. 
The time consumed in memorizing one of these lists, maintaining 
correctness of meanings and relative positions of all words, was se- 
cured at ten periods, for twelve days. The lists were used a full 
year after their preparation. The external conditions during the 
progress of this test were excellent, being practically unvaried from 
day to day. The entire twelve days were devoted to experimenta- 
tion, from 7 :30 a.m. till 11 p.m., excepting for meals, 8 to 8 :30 
a.m., 12 to 1 :30 p.m., 6 :30 to 7 :30 p.m. The same thing was done at 
the same hour each day. This program was adhered to without 
change and without interruptions, so that none but constant causes 
influenced any of the trials. But the increasing monotony of the 
task may have somewhat affected the later periods of the last few 
days. The results, in Table XXII., are in terms of the average num- 
ber of seconds required to learn each list fully. 

Table XXII. Memory — 10 Geeman Words and Their Meanings. 



No. of 
Words 



7 A.M. 
Time P.E. 



8:30 
Time. P.E. 



10:00 
Time. P.E. 



11:30 
Time. P.E. 



1:30 P.M 
Time. P.E. 



3:00 
Time P.E. 



120 



371 10.26 390 14.34 386 10.09 434 16.89 475 12.11 460 11.21 



No. of 
Words. 



120 



4:30 6:00 

Time. P.E Time. P.E. 



445 15.19 431 15.02 



7:30 
Time. P.E. 



444 16.72 



9:00 
Time. P.E. 



544 15.13 



10:30 
Time. P E 



613 17.33 



This table shows some clear variations. The morning is by far 
the best ; a slump occurs between 1 p.m. and 3 :30 p.m. ; then a level 



COURSE OF MENTAL EFFICIENCY 



51 



period till 8 p.m. ; after which there is a decided drop. The normal 
curve of the author's subjective feelings follows a like course, save 
as to the degree of the night drop. The other tests of memory on 
myself should not have the same weight as these figures, though, as 
a matter of fact, they corroborate them. 

This subject used also lists of eight single numerals for visual 
memory, exposing at a uniform rate the successive figures on cards. 
Three of these were used each period for thirty days. The first 
period and the last two were liable to little interruption; the others 
to more. Only the average number of mistakes is shown in the 
following results : 

7 A.M., 0.8 ; 10 A.M., 1.9 ; 1 P.M., 1.8 ; 4 P.M., 1.8 ; 7 P.M., 1.5 ; 10 P.M., 1.2. 

The middle three can not be compared with the others, for the 
reason already stated, but show no differences among themselves. 
The first period is most probably the best. 

Subjects III., IV., V. and VI. pursued the same method with lists 
of nine figures. They counted their own mistakes, cases of incorrect 
order being called erroneous as well as wrong figures. The P.E.'s 
are calculated from the whole series, though some practise effect is 
apparent— but two days were omitted for III. The results are the 
first in Table XXIII. 



Table XXIII. Memory — 9 Figures and 16 Words. 



Figures. 


No. of 
Lists. 


7-9 A.M. 
Misses. P.E 


12-2 P.M. 
Misses. P.E. 


5-7 P.M. 
Misses. P.E. 


9-11 
Misses 


P.M. 


Subject. 


P.E. 


III. 

IV. 

V. 

VI. 


30 

30 
36 
30 

32 


1.5 
3.1 

5.8 
3.3 

3.4 


0.38 
0.53 
0.37 
0.40 

0.42 


1.2 
2.6 
4.0 
3.1 

2.7 


0.39 
0.32 
0.42 
0.34 

0.37 


1.1 
3.1 
3.3 

2.0 

2.4 


0.26 
0.33 
0.54 
0.48 

0.40 


1.8 
3.4 
4.7 
3.9 

3.4 


0.27 
0.34 
0.47 
0.39 

0.37 


Words. 












I. 
II. 
A 


48 
48 
48 


8.1 
4.0 
6.2 


0.58 
0.23 
0.28 


10.4 

9.0 


1.71 
0.44 


9.4 
6.1 
6.1 


0.82 
1.10 
0.29 


9.8 

7.2 
7.1 


0.91 
0.55 
0.31 


Figures. 












"^ Visual 

•ji* Auditory... 
== Vis.-Aud... 


24 
42 
16 

27 


1.5 
1.3 
1.0 

1.3 


0.18 
0.31 
0.32 

0.27 




2.5 
0.7 
1.3 

1.5 


0.39 
0.18 
0.28 

0.28 


3.1 
2.2 
1.3 

2.2 


0.76 
0.52 
0.35 

0.54 



Subjects I., II. and A were tested in visual memory with words 
— four groups of four words each, every period. The words of a 
group were more or less logically connected, as they were cut from 
newspaper sentences. These partial clauses had been pasted on 



52 DIURNAL COURSE OF EFFICIENCY 

separate strips of cardboard, for ready exposure, as in the other 
memory test. Henee each effort of the memory was an attempt to 
recall sixteen words thus arranged and handled. The results in the 
middle section of Table XXIII. are in terms of the mistakes. 

For subject A, results from the following tests are then shown: 
(1) visual memory, with lists of nine figures; (2) auditory, similar 
lists being read aloud to the subject; (3) auditory-visual, the figures 
being both heard and seen simultaneously. 

The first group, consisting of the four subjects III., IV., V., VI., 
as a whole conforms the most closely to the type of efficiency reach- 
ing a significant maximum in the midday periods. But in the other 
subjects the tendency is strong to a morning maximum and to a noon 
minimum, in the case of the males, and a night minimum for the 
females. 

The auditory memory tests with numerals were given to the 
Teachers College female students, six lists being used at each period 
for one day ; and to subject VII., three lists being used at each period 
for four days. Results : 





Mis. 


B. 


P. E. 


Mis. 


VII. 


P. E 


9 A.M., ! 


9.0 




0.7 


4.5 




0.6 


2 M., j 


6.9 




0.6 


4.5 




0.8 


4 P.M., 


7.0 




0.5 


4.8 




0.5 



Newness of the test at the first period and practise effect at the 
others tend to make these differences problematical in the case of the 
young women, while they seem chance differences in case of sub- 
ject VII. 

Larguier 1 memorized passages of ten sentences from Racine and 
measured results in number of seconds required to do the learning, 
obtaining, before coffee, 316 (av. of 16 days) ; before lunch, 349 (8 
days) ; after lunch, 341 (7 days) ; before dinner, 345 (9 days) ; after 
dinner, 280 (5 days). In reproduction of the passages 24 hours 
later, he found the best results after dinner and the worst at the 
first period. Besides being the record of only one subject these re- 
sults fall under the criticism explained early in this paper (p. 2), in 
that, as seen from the differing figures in parentheses, valid results 
were expected, in short series, from experiments where every period 
of the maximum number of days reported had not been duly used. 2 

1 ' Note sur les Variations de la Memoire au Cours de la Journee/ L'Annee 
Psych., 8: 205-213. 1901. 

- This is strikingly shown in another series, of ostensibly 14 days' length, 
testing the effect of alcohol on memory, where only rarely do two experiments 
seem to have been taken the same day before and after lunch. 



COURSE OF MENTAL EFFICIENCY 53 

Thus no account was taken of the inevitable difference of efficiency 
between one day and another. 

M. C. Schuytens, in an article soon to be mentioned, finds memory 
in school children, in class tests, to be dependent on whether their 
first trials are made in the morning or in the afternoon. In other 
words, it is entirely a matter of interest with them ; they lose interest 
after the first trial. 

The total outcome as to memory must be considered a negation 
of the existence of a simple diurnal memory curve, though this point 
will be touched again in the subsequent. discussion of fatigue. 



II. The More Complex Mental Activities 

1. Arithmetic 

This has long been a favorite test, supposedly of general mental 
efficiency. This special preference has been due largely to the tradi- 
tional conception that no other school branch is so difficult for the 
ordinary student to master, that it is more purely logical in nature, 
and partly to the experimental evidence furnished by certain in- 
vestigators of the question of school fatigue. 

It is scarcely allowable at the present day to accept an arith- 
metical test as a measure of general mental efficiency. The mere 
fact of difficulty does not prove it to be such a measure ; rather must 
the causes of this difficulty first be determined by means of refined 
empirical analysis, which can not be attempted here. An arith- 
metical test does no doubt call for the exercise of various important 
mental powers, such as attention, discrimination, memory, etc. ; but 
though these generic terms are convenient, their application to con- 
crete cases requires more particularization and qualification, as 
already remarked. The attention, discrimination and memory in- 
volved in an example in multiplication are not quite the same proc- 
esses as have been studied in the preceding tests. For our present 
purpose, the arithmetical tests are to be regarded simply as measures 
of efficiency in a rather complex and very practical sort of mental 
work. 

1. Addition. — Subject I., for 28 days at the periods shown in the 
lowest part of Table XXIV., added six columns (25 figures each) as 
rapidly as possible, timing with a stop-watch. The average time in 
seconds is shown. The first six subjects used ten columns (15 figures 
each) : A used six columns. Some correction was made for practise 
in the first five days. 



54 



DIURNAL COURSE OF EFFICIENCY 



Table XXIV. Addition — Columns of 15 Figures. 



Subject. 


Total No. of 
Columns. 


I. 


140 


II. 


120 


III. 


120 


IV. 


100 


V. 


120 


VI. 


100 


Average. 


117 


A 


84 



7-9 A.M. 
Time. P.E. Mis. 



99.4 

110.2 

89.5 

66.3 

105.2 

122.3 



1.00 
1.11 
1.28 
0.55 
0.99 
1.78 



1.2 
0.8 
1.0 
0.6 
1.3 
1.1 



98.8 1.11 
112.3 2.4 



1.0 
1.2 



12-2 P.M. 
Time. P.E. Mis. 



91.9 0.91 0.6 
99.1 1.44 0.7 
87.3 1.13 0.7 

64.7 0.78 0.8 

90.8 0.81 0.6 
119.4 1.81 1.4 



5-7 P.M. 
Time. P.E. Mis. 



92.6 0.86 1.4 

106.9 1.32 0.9 

86.0 0.90 0.7 

63.6 0.78 0.6 

99.2 0.88 1.0 

123.0 1.58 1.0 



92.2 1.15 0.6 95.2 1.06 0.9 
— 106.7 2.1 1.1 



9-11 P.M. 
Time. P.E. Mis. 



97.0 0.89 0.9 
109.2 1.67 1.1 
85.3 0.90 1.5 
69.2 1.52 0.6 
98.8 0.69 1.2 
116.9 1.79 1.2 



96.1 1.24 1.08 
107.6 2.5 1.4 



Cols, of 
25 Figs. 


7 A.M. 


10 A.M. 


1P.M. 


4 P.M. 


7 P.M. 


10 P.M. 


I. 150 


29.6 0.221.1 


28.4 0.281.0 


29.2 0.281.0 


28.5 0.29 0.8 


28.0 0.241.0 31.0 0.291.0 



The fact found here is a higher efficiency at the noon period and 
a lower efficiency in the morning than at the other periods, with the 
usual individual divergencies rather minimized. Accuracy pursues 
the same course as speed, which is noteworthy when compared with 
its tendency in the other tests. In the lower case of subject I., the 
10 a.m., 1 and 4 p.m. periods were affected by occasional interruption. 

Subject VII., in an uncompleted series of four days, took this 
test at 9 a.m., 12 m. and 4 p.m., and made this record: 

232 (P.E., 3.2); 215 (2.1); 227 (2.9). 

Each member of group B was given 24 of these 15-figure lists, 
and 240 seconds in which to add them. Their results are expressed 
in terms of the average number of columns done and the P.E. : 

15 (1.4); 14 (1.3); 15 (1.3). 

This is a chance order. Here, as in memory, the first trial is at a 
disadvantage because of newness of the test, while the others are more 
favored by practise. 

2. Multiplication,' — In mental multiplication, subject I. for 
twelve days, under the very favorable conditions described for the 
German words memory test, used two-place numbers after excluding 
0, 1, 2 and 5 — though 5 was used in hard combinations. Being a 
poor visualizer, the author found this to be a sufficiently difficult 
test. At each period, three pairs (on some days four) of such 
numbers were multiplied, and the time taken as before. 

The first two are the periods of highest ability; from 1:30 p.m. 
to 3 p.m., at 6 p.m. and again at 10:30 P.m. occur the points of 
greatest inefficiency. This very closely follows the diurnal curve 
of subjective feeling alluded to above. It is nearer that for memory 
than for addition, though really comparable figures are not at hand. 



COURSE OF MENTAL EFFICIENCY 



55 



The order shown is heightened in validity when the mistakes are 
also considered; there is no inverse relation here. 

Table XXV. Mental Multiplication — Numbers of 2 Figures. 



Subj. 


No. 


7:00 A.M. 
Time. P.E. 


8:30 A.M. 
Mis. Time. P.E. Mis. 


10:00 A.M. 
Time. P.E. Mis. 


11:30 A.M. 
Time. P.E. Mis. 


I. 


40 


37.6 2.4 


.50 


34.7 1.6 .50 


39.7 2.5 .63 


41.8 1.7 .50 


Subj. 


No. 


1:30 P.M. 
Time. P.E. 


3:00 P.M. 
Mis. Time. P.E. Mis. 


4:30 P.M. 
Time. P.E. Mis. 


6:00 P.M. 
Time. P.E. Mis. 


I. 


40 


4.80 2.6 


.70 45.3 2.6 .83 


41.0 1.8 .60 


47.1 2.4 .71 


£ 


ubj. 


No. 


7:30 P.M. 
Time. P.E. Mis. 


9:00 P.M. 
Time. P.E. Mis. 


10:30 P.M. 
Time. P.E. Mis. 


I. 


40 


39.8 1.9 .53 


41.7 1.8 .63 


47.0 2.6 .73 



In the following section (p. 75), reference will be made to work 
in addition done by Roemer, who finds the first of four morning 
periods the best; and by Thorndike (p. 85), who also found the 
ability slightly the best then. The latter, in mental multiplication, 
found in a very short series the night period a little better for 
adults; while in written multiplication a very extensive test of 
school children (750) favored the morning. 

2. Translating French; Scoring Death Records 

Subject I., under the excellent conditions of all-day experimenta- 
tion described above, translated French at seven different periods 
of an hour each, every day for twelve days. It would seem at first 
thought that translation by mere reading is a better test than that 
by writing, since the latter involves a motor element. However, 
the former is subject to a subtler and no less vitiating complication. 
All that one aims to do by the reading method is to get the meaning, 
and that usually amounts to merely sensing the meaning. This 
process is so indefinite and the quality of the results so indifferently 
estimated as to make unreliable all objective measurement based on 
the number of sentences thus subjectively rendered. That is, the 
work at those periods of the day when feelings of fatigue are most 
pronounced would unconsciously be slurred over, while at those 
times when one is most conscientiously sensitive to his duty it would 
be relatively slow. The net result would be a lessening of the 
diurnal differences. No such fast-and-loose interplay can well be 
indulged in when the product is in sight, and for this reason the 
other method was selected. Scientifically unsatisfactory, it yet gives 
an idea of what might be expected in the practical matter of written 
translation. 



56 DIURNAL COURSE OF EFFICIENCY 

Table XXVI. Fbench Translation — Sentences Weitten Pee Houe. 



Sub- 
ject, 


9:00-10:00 A.M. 
No. P.E. 


10:30-11:30 
No. P.E. 


2:00-3:00 P.M. 
No. P.E. 


3:30-4:30 
No. P.E. 


5:00-6:00 
No. P.E. 


8:00-9:00 
No. P.E. 


9:30-11:30 
No. P.E. 


I 


50 0.88 


51 1.03 


54 1.17 


55 0.77 


54 1.12 


56 1.02 


57 0.44 



The morning work is slowest, the afternoon medium, and the 
night swiftest. In accounting for the higher night efficiency, the 
following factors seem to figure in the result and to be of weight in 
the order named: (1) quicker motor functioning; (2) practise effect; 
(3) habit; (4) end-glow. 

In examining the 36,000 death records, reported earlier in the 
paper, ten days were consumed by subject I. at the New York City 
Health Department offices. Work was begun promptly at 9 a.m. 
and continued without interruption till 12:45 p.m.; beginning at 
1 :15 p.m. there was no break till 4 p.m., when the office closed. Dur- 
ing this time, tab was kept on the exact number of records handled 
every fifteen minutes, and the average scores obtained are in the 
following table. The fourth and fifth results are estimated from 
work of three quarters of an hour in length. 

Table XXVII. Death Recoeds. 
Aveeage Numbee Examined Each Foueth of an Houe. 



I. 



10 



9-10 A.M. 
No. P.E. 



138.6 1.06 



10-11 A.M. 
No. P.E. 



135.0 1.34 



11-12 A.M. 
No. P.E. 



133.9 1.23 



12-1 P.M. 
No. P.E. 



131.4 2.39 



1-2 P.M. 
No. P.E. 



133.1 2.11 



2-3 P.M. 
No. P.E. 



130.1 2.03 



3-4 P.M. 
No. P.E. 



142.1 1.79 



There is a decided falling off after the first hour which continues 
till noon intermission ; then a slight recovery, followed by the lowest 
point reached, which is itself succeeded by the highest point. This 
curve can not be said to follow, throughout its whole course, that 
of any other measured activity of this subject. This is not odd, as 
the operation involved was a very complex one. Five things had to 
be noted in different parts of the death certificate — cause, time and 
season of death, age and sex. While being located properly on the 
score sheets — a process again involving much discrimination — they 
had to be carried in mind or else a second look was required. Judg- 
ment was also required in the work; but memory and movement 
were apparently the most telling elements in determining the curve. 
Good memory favored a strong beginning in the morning and good 
motor rate a strong ending in the afternoon, while the period from 
1 p.m till 3 p.m. was specially unfavorable to both. The impulse to 
finish a certain number before four o'clock, if possible, was always 
too great to be resisted, even when note was taken of the accelerated 



COURSE OF MENTAL EFFICIENCY 57 

rate and it was felt that the results were being unduly affected. 
Yet it must be recalled that every effort was made throughout the 
day to do the utmost possible consistent with accuracy. End-glow 
has often established its claim to recognition, but no special practical 
use of it suggests itself. 



l teto v 



3. School Examinations and School Marks 

Rice 1 conducted some very extensive tests in spelling and arith- 
metic, to ascertain the relative values of different methods of admin- 
istration and teaching, and other points of educational import. The 
arithmetical investigation was carried on with 6,000 children, of 
eighteen schools, in seven cities, and consisted in giving certain 
examples to be worked, the total outcome of which was then scored 
up in several ways— (a) per cent, correctly done; (&) per cent, with 
principle correct: (c) average number of mechanical errors made. 
About half of the tests were given in the morning and half in the 
afternoon. 

As far as Rice's work touches the present problem, his ideas are 
fully set forth in the following quotation, it being understood that 
the table referred to by him shows only incidentally the times of day 
when the schools were examined, and does not collate the results 
quantitatively from this point of view, which is investigated only 
in the desultory fashion betokened by his remarks : 

The idea is generally accepted that an examination in arithmetic given in 
the morning will show much more favorable results than one given in the 
afternoon, and it, therefore, might be supposed that the schools that did best 
had been examined in the morning, and vice versa. When the table was ex- 
amined from this standpoint the indications appeared to favor the theory; but 
the quantitative aspect has certainly been exaggerated. Looking at the facts 
we find that ... the first three schools of city I. were examined in the morning 
and did well. The fourth of that city was examined in the afternoon and also 
did well. The point of particular interest is the fact that the school by be- 
ing examined in the afternoon did not lose its classification (rank). . . . 
Thus while there seems to be some advantage in an examination in the morning, 
the figures appear to leave no doubt that a school that can do well in the morn- 
ing can also do well in the afternoon, and conversely. ... I have heard it 
stated that the difference between a morning and an afternoon examination will 
probably reach 20 per cent. 

His table is extensive, showing results separately for each school 
grade examined. By averaging together all grades of each school, 
the figures of Table XXVIII. were obtained as measures of the 
different schools as wholes. Eight were examined in the morning 
and ten in the afternoon ; to get equality, the records of schools II. 

1 ' Educational Research,' Forum, 34: 281-297. 1902. 



58 



DIURNAL COURSE OF EFFICIENCY 



and V., falling practically at the median for all the afternoon 
schools, were omitted. 



Table XXVIII. A Test in Akithmetic- 


—Revision 


after Rice. 




School. 


Morning. 




Afternoon. 




City. 


Work 
Correct. 


Principle 
Correct. 


Mechanical 
Errors. 


Work| 
Correct. 


Principle 
Correct. 


Mechanical 
Errors. 


III. 


1 


80.0 


83.1 


3.7 








I. 
I. 
I. 
I. 


1 

2 
3 
4 


76.6 
69.3 
67.8 


80.3 
75.1 

72.2 


4.6 
7.7 
6.1 


64.3 


70.3 


8.5 


III. 


2 








54.4 


58.9 


7.4 


IV. 
IV. 
IV. 

IV. 


1 

2 
3 
4 


55.1 
51.5 


58.4 
57.6 


5.6 
10.5 


53.9 

42.8 


58.8 
48.2 


8.3 
11.2 


VI. 
VI. 
VI. 


1 

2 
3 


39.0 


42.9 


9.0 


36.5 
36.0 


43.6 
42.5 


16.2 
15.2 


VII. 
VII. 
VII. 


1 
2 
3 


40.5 


45.9 


11.7 


36.5 
25.3 


40.6 
31.5 


10.1 
19.6 


Averages of the 8 
Schools' Averages. 


60.0 


64.4 


7.4 


43.7 


. 49.3 


12.1 



A giance at this table shows a decided superiority of the morning 
over the afternoon schools, the latter doing only about 70 per cent, 
as well as the former, taking all three modes of scoring into consid- 
eration. This would certainly have been observed by Dr. Rice if 
he had thought it worth while to make other than a casual com- 
parison. Several of his quoted statements seem unhappily framed, 
in the light of this revised tabulation. It may be urged against this 
revision that the best cities were tested mostly in the morning and 
the poorest mostly in the afternoon. Of course there is no way of 
knowing offhand whether this is true or not, but it will be found by 
examination of the table that the percentage of difference still re- 
mains considerable when only schools of the same city are compared 
with each other. When the extensiveness of the experiments and 
the decisiveness of the results are both considered, such figures have 
no small importance for the view that children reach their maximal 
period of customary efficiency earlier than adults. 

The writer attempted to get school marks of different classes 
in the same branch, under the same teacher, but meeting at different 
times of day, in the New York City High Schools. Only one school 
was found in which the conditions were favorable. In that about 
fifteen teachers had from two to four classes of the kind required, 



COURSE OF MENTAL EFFICIENCY 59 

and to each of these teachers was given written information as to 
the problem and its pedagogical bearing, together with the nature 
of the data desired, and a blank form upon which the marks could 
be readily copied. It would have taken a live teacher about fifteen 
minutes to transcribe the marks of four ordinary classes, whereas 
it took the author a day — after getting the school located — to do his 
part : as result, one teacher responded with four classes. 

Two first-year morning classes in botany, 23 pupils each, aver- 
aged 62 and 67, while two in the afternoon, of 24 and 25 pupils, 
averaged 61 and 62. This whole case is introduced to show the need 
of a more general and extensive sympathy with scientific efforts. 
While only 78 per cent, of the manufacturers and 80 per cent, of 
the physical directors and athletes failed to make a response of any 
sort, 92 per cent, of the educating class itself took this frigid attitude, 
and that, too, when less was individually required. The loss to 
science is not great in regard to the school marks, as the bases of 
grading, with different teachers, are quite variable factors. 

4. Students' and Authors' Preferred Hours for Work 

The work of 'Shea's, 1 incidentally mentioned above, is largely 
based on the answers received to a questionnaire sent to the students 
of the University of Wisconsin. Two of the questions were — Dur- 
ing what hours of the day are you at your best ? and, When are you 
dullest? The total number of answers received is not stated, but 
the number treated is 316. To this topic, in the text, he devotes little 
more than a page, from which the following quotations are made : 
"Practically all those who reported testified that their minds worked 
best in the forenoon, eighteen reported being best in the afternoon, 
while two found that they could accomplish more at five o'clock in 
the morning than at any other hour. The best hours ranged from 
7 to 12 in the forenoon while the choicest period of the day is from 
9 to 11." It is unfortunate that the second question was entirely 
ignored, though we are just as much interested in knowing its 
answer. To thus omit half a fact seems unscientific. 

Quoting again (p. 195), "There can be little doubt that for most 
people the morning hours are most profitable to be devoted to dili- 
gent, concentrated study. The afternoon hours can be employed 
to greater advantage in duties demanding less energizing of the will ; 
while in an ideal program the evening hours will be spent almost 
wholly in relaxation. ... 2 students reported not studying be- 
yond 8 (at night); 44 worked until 9; 187 until 10; 70 until 11; 
9 until 12 ; and 1 until 1. . . . Forty of those who studied very 

11 Aspects of Mental Economy,' Bui. of Univ. of Wis., 2: 34-198. 1901. 



60 DIURNAL COURSE OF EFFICIENCY 

late into the night testify that the knowledge they acquired stayed 
with them ; 58 said that in the morning it, like the Arab, had folded 
its tent and silently slipped away. ' ' 

This oriental allusion recalls what Dr. J. M. Scott, Professor 
of Greek in Northwestern University, recently 1 said so directly to 
the contrary in addressing his class on 'burning the midnight oil'. 
"In olden days," he stated, "the Persians congregated at daybreak 
to pursue their studies; but nowadays the great scholars pore over 
their books at night. In the morning one's eyes are not clear, his 
head still is numb from sleep, and he is in no condition for mental 
work. Because of lack of illuminating facilities the ancients were 
obliged to study in the early morning. Although I would not urge 
any of you to refrain from rising early, I would advise you to do 
your studying at night." 

It is a question for serious consideration whether an occasional 
sacrifice to overstudy should not be made rather than that such an 
arbitrary rule of ten o'clock retirement should be imposed as exists 
at most of our women's colleges. When one gets 'into the swing' 
he can often accomplish more in six or eight consecutive hours of 
night work than in double that number of hours of day work done in 
bits, as it often is. Whenever a person can work with the least 
expenditure of energy is the proper time for him to do so. 2 There 
seems no more reason in trying to fit all types of students to one 
sort of study-hour jacket than in attempting to place one kind of 
instruction-plan coat upon all kinds of developing individualities. 
Authors have learned this general fact by experience and take ad- 
vantage of it in their work, if the following account of them is 
typical, as it seems to be. 

Hundreds of biographies 3 were scanned for the occasional words 
treating the matter of authors' preferred hours for composition. 
Some 160, odd, cases were found, definite enough for accurate use, 
and of these 160, even, of the best were selected for reporting here. 
These distributed themselves diurnally in this manner: morning 
composers (6 a.m. to 2 p.m.), 55, or 34 per cent.; afternoon (2 to 
7 p.m.), 2, or 1 per cent.; night (7 to 12 p.m.), 17, or 12 per cent.; 
after midnight (12 to 6 a.m.), 9, or 6 per cent.; morning and after- 
noon (6 a.m. to 7 p.m.), 27, or 17 per cent.; morning and night (6 

starch 24, 1905. 

2 See Hamerton's Intellectual Life, pp. 380-400, for instructive treatment 
of this question. 

3 About 100 volumes were examined in this search. The two of most value 
were Dr. Hugo Erichsen's Methods of Authors, 1894, and Aspects of Authorship, 
by F. Jacox, 1872. 



COURSE OF MENTAL EFFICIENCY 61 

a.m. to 2 p.m. and 7 to 12 p.m.), 6, or 4 per cent.; afternoon and 
night (2 to 12 p.m.), 4, or 3 per cent.; whole day (6 a.m. to 12 p.m.), 
37, or 23 per cent. Some writers were included whose actual work- 
ing hours were secured, but not their expressly preferred hours. 
Some, who were assigned to the first, fifth or last group, might 
almost as correctly have been put in the 'night' group, for one reason 
and another, and this would raise the percentage of the latter some- 
what. Secondary preferences are shown in parentheses in the de- 
tailed list now to be given. The chief field of each one's activities 
is only partially indicated in most of the cases. The letter F, in 
parentheses, means 'female.' The lists are arranged alphabetically. 

Morning: J. Addison (Eng. essayist), G. von Amyntor (Ger. 
novelist), L. A. Banks (Am. clergyman and author), V. Bliithgen 
(Ger. novelist — night), C. Bronte (Eng. novelist and poet — F), 
E. Bronte (Eng. novelist and poet — F), M. Cawein (Am. poet), 
T. Chalmers (Eng. theologian and journalist), G. M. Craik (Eng. 
novelist— F), C. Deslys (Fr. novelist), C. Dickens (Eng. novelist), 
J. Dryden (Eng. poet), R. W. Emerson (Am. philosopher and essay- 
ist—night), M. Eytinge ( — — poet and novelist— F), K. Field (Am. 
novelist — F), K. Frenzel (Ger. journalist— night), 0. F. Genischen 
(Ger. dramatist), E. Gibbon (Eng. historian), J. W. Goethe (Ger. 
poet), E. Gosse (Eng. poet and critic— night), E. E. Hale (Am. 
essayist), R. Hamerling (Austrian novelist), 0. W. Holmes (Am. 
poet and humorist), W. D. Howells (Am. novelist), V. Hugo (Fr. 
novelist), L. Hunt (Eng. poet — night), W. Irving (Am. novelist), 
D. W. Jerrold (Eng. dramatist and journalist — night), I. Kant 
(Ger. philosopher), T. B. Macaulay (Eng. essayist), H. Martineau 
(Eng. novelist — F), (J.) B. Matthews (Am. dramatist and critic — 
night), J. Miller (Am. poet), J. Milton (Eng. poet — afternoon), 
A. Niemann (Ger. novelist), A. Pope (Eng. poet — day), L. de la 
Ramee (Eng. novelist— F), E. Richebourg (Fr. novelist), J. P. 
Richter (Ger. poet), L. de Sacher-Masoch (Fr. story writer — after- 
noon), J. Scherr (Swiss novelist and historian), Sir W. Scott (Eng. 
novelist), W. G. Simms (Am. poet— night), F. R. Stockton (Am. 
novelist), J. Taylor (Eng. poet and novelist— F), W. M. Thackeray 
(Eng. novelist), A. Thuriet (Fr. novelist), M. Thompson (Am. critic 
and essayist), E. Vely (Ger. novelist— F), P. Virgil (Latin poet), 
R. Waldmueller (Ger. novelist), D. Webster (Am. statesman), E. 
"Wichert (Ger. novelist), C. M. Yonge (Eng. novelist— F), C. Kings- 
ley (Eng. clergyman and novelist— night). 

Afternoon: S. 0. Jewett (Am. story writer— F), A. Traeger 
(Ger. poet). 
5 



62 DIURNAL COURSE OF EFFICIENCY 

Night: V. Alfieri (Italian dramatist), W. B. Blake (Eng. poet — 
after midnight), K. S. Bonner (Am. story writer and novelist — F), 
R. S. Cabanis (Ger. humorist— after midnight), Wm. Collins (Eng. 
poet), J. Fastenrath (Ger. and Span, poet), R. E. Francillon (Fr. 
novelist and journalist — afternoon), F. Friedrich (Ger. novelist), 
W. A. Hammond (Am. novelist — after midnight), T. Hardy (Eng. 
novelist — day), J. C. Harris (Am. humorist and journalist — day), 
H. Herberg (Ger. novelist), T. Hood (Eng. poet and humorist- 
day), S. Johnson (Eng. essayist and lexicographer— day), C. Lamb 
(Eng. poet — after midnight), M. J. Preston (Am. poet — F), S. 
Rogers (Eng. poet), P. K. Rossegger (Austrian novelist), R. B. 
Sheridan (Eng. dramatist), R. Southey (Eng. poet — day). 

After midnight: H. de Balzac (Fr. novelist), Lord Byron (Eng. 
poet), S. T. Coleridge (Eng. poet), T. De Quincey (Eng. essayist), 
J. Fane (Eng. poet), Lord Jeffrey (Eng. poet), E. A. Poe (Am. poet 
and story writer), H. Rollet (Austrian poet— night), F. Schiller 
(Ger. poet— night). 

Morning and afternoon: L. Anzengruber (Austrian story writer), 
R. Baumbach (Austrian poet), J. Burroughs (Am. naturalist), T. 
Carlyle (Scot, essayist and historian), J. Claretie (Fr. novelist), 
M. D. Conway (Am. essayist), F. Dahn (Ger. historian and poet), 
G. M. Fenn (Eng. novelist), P. Galen (Ger. novelist— night), A. 
Glaser (Ger. novelist — night), R. von Gottschall (Ger. novelist and 
journalist), M. Greif (Ger. poet), L. Habicht (Ger. novelist), T. W. 
Higginson (Am. novelist and essayist), L. Larcom (Am. poet — F), 
H. Malot (Fr. novelist), T. Moore (Eng. poet), J. Nordmann (Ger. 
novelist and journalist), U. Prynne (Eng. controversialist), W. H. 
Riehl (Ger. novelist), E. P. Roe (Am. novelist — night), J. Stinde 
(Ger. satirist), C. Thaxter (Am. poet — F), J. T. Trowbridge (Am. 
novelist), J. G. Whittier (Am. poet), A. von Winterfeld (Ger. 
humorist), J. Wolff e (Ger. poet). 

Morning and night: R. Burns (Scot, poet), 0. Goldsmith (Eng. 
poet and novelist), N. Hawthorne (Am. novelist), Plato (Gr. philos- 
opher), F. W. Robertson (Scot, clergyman and author), S. Smith 
(Eng. poet and critic). 

Afternoon and night: T. Campbell (Scottish poet and novelist), 
W. Hazlitt (Eng. critic and essayist), J. Rousseau (Fr. philosopher 
and educator), A. Streckfuss (Ger. novelist). 

Whole day: L. M. Alcott (Am. novelist— F), H. H. Bancroft 
(Am. historian) 'Venerable Bede' (Eng. author), E. Bulwer-Lytton 
(Eng. novelist and poet), W. Carleton (Am. poet), T. Carte (Eng. 
historian), Wilkie Collins (Eng. novelist), Delambre (Fr. philos- 
opher), A. L. G. N. De Stael (Fr. novelist— F), G. Ebers (Ger. 



COURSE OF MENTAL EFFICIENCY 63 

novelist — night), J. Fiske (Am. historian and essayist), P. H. Hayne 
(Am. poet), J. Hogg (Scot, poet and biographer), J. Keats (Eng. 
poet), W. S. Landor (Eng. poet), S. Lanier (Am. poet and novelist), 
0. von Leixner (Ger. poet, historian and novelist — night), P. Lindau 
(Ger. novelist), H. W. Longfellow (Am. poet), Mazerai (Aus. his- 
torian), A. Meissner (Austrian novelist— night), J. L. Motley (Am. 
historian), J. Payn (Eng. novelist), P. Petrarch (Italian ecclesiast 
and poet), W. H. Prescott (Am. historian), B. W. Proctor (Eng. 
poet), F. Rabelais (Fr. educator and humorist), L. von Ranke (Ger. 
historian), J. W. Riley (Am. poet), W. Robertson (Eng. historian), 
P. B. Shelley (Eng. poet), K. Stelter (Ger. poet— night), H. B. 
Stowe (Am. novelist— F) , H. D. Thoreau (Am. author), E. M. 
Vacano (Ital. author), J. Wilson (Scot, essayist, novelist and poet), 
W. Wordsworth (Eng. poet). 

Numerically, morning stands easily in the lead among the different 
groups, and this precedence might be emphasized if those persons 
could be segregated from the fifth, sixth and eighth groups who 
were obliged by financial necessity, or social custom, to scatter their 
work over such extensive periods of the day. 

But an accurate estimate of the night workers will show this 
general group a closer second to the former than appears at first 
sight. Again we must make allowance for those included in groups 
6, 7 and 8 who would preferably work only at night if composition 
depended only on inclination. Fourteen, outside of the distinctively 
night groups, have indicated a night choice, and should likely be 
classed there, as they have for the most part stated that this period 
seemed the best for the 'creative' part of their labor, at least, or was 
preferred in early life. Psychologically, it may not be entirely true 
that imaginative work is more creative than certain other kinds, but 
it is usually so considered among the writers themselves. 

If we take the 'internal evidence' of the groups themselves, it is 
possible to get a little added light on this matter of the best times 
for different sorts of composition. That is, if the poets and novelists 
are roughly designated as an imaginative class, and the historians, 
clergymen, essayists, critics, journalists, philosophers, etc., as a 
broader, intellective class, we shall find the former predominant in 
the morning and night groups and the latter in the day ones. Entire 
confidence can not be placed in this division, as the original assign- 
ment of 'fields of activity' to the various writers is not thoroughly 
exact, in that it is much too limited per individual. But certain 
special groups tend to confirm the conclusion. Thus, of thirteen his- 
torians mentioned, eleven occur in the all-day section; and of the 



64 DIURNAL COURSE OF EFFICIENCY 

after-midnight workers all are of the imaginative type— if De 
Quincey 's product is allowed to be prose-poetry, as it is often styled. 

While the theory that night furnishes the best time for original 
composition is thus at least strongly suggested, it seems to the pres- 
ent writer lacking in ground to support such extreme views as have 
been advanced by some. De Quincey is authority for this state- 
ment of C. Lamb: "No true poem ever owed its birth to the sun's 
light. The mild internal light, that reveals the fine shapings of 
poetry, like fires on the domestic hearth, goes out in the sunshine. 
Milton's Morning Hymn in Paradise, we would hold a good wager, 
was penned at midnight, and Taylor's rich description of a sun- 
rise smells decidedly of a taper." This view, besides being 
worded possibly for effect, is influenced by his own actual prac- 
tise in regard to night work. Erichsen, alluded to above, is a 
whole-hearted convert to the theory, though no little could be 
cited against its unconditional adoption from his own book. 
He remarks that Lamb's tasks "courted the aid of evening, which 
by means of physical weariness produces a more luxurious state 
of repose than belongs to the labor hours of day. . . . They 
[the words 'physical weariness'] almost exactly define that un- 
natural condition of the body which on other grounds appears to 
be proper to the unnatural exertion of the mind." The extent to 
which he carries the latter idea may be gathered from a reference 
of his to Scott, in another connection. Scott had said of his own 
review of Ritson's Caledonian Annals that "no one who has not 
labored as I have done on imaginary topics can judge of the comfort 
afforded by walking on all fours, and being grave and dull. " " There 
spoke the man," says Erichsen, "who habitually and without arti- 
ficial help drew upon his imagination at the hours (in the morning) 
when instinct has told others that they should be employing, not 
their fancy, but their reason. So Scott compelled himself to do 
unhealthy or abnormal work without the congenial help of abnormal 
conditions. ' ' 

Such ideas quite ignore the fact of individual differences— that 
many have accomplished as good work in the daytime as those who 
wrote at night. They also ignore the negative opinions of other 
writers couched in as positive terms as the preceding. Only one of 
these, having more empirical basis than the rest, will be mentioned. 
G. M. Fenn, shown in the above morning-afternoon list, after experi- 
menting with different methods for some years, off and on, decidedly 
prefers the daytime. He admits that brilliant work has often been 
done at night, but, after trial, found the results of a month's day 
work more satisfactory than an equivalent period of night work. 



COURSE OF MENTAL EFFICIENCY 65 

Parenthetically it may be noted here that the last reference sug- 
gests the practical problem of how far regular habits of work have 
proven beneficial, compared with mere mood-composition. My notes, 
having bearing on this, are too numerous to make it worth taking 
up in the short space to which it would have to be confined. 1 This 
much seems true, however, that the night workers tend markedly to 
be mood-workers, while those of the day tend more to regularity in 
production. But that the quality of the latter work is better is not 
true, though the quantity may possibly be greater. 

Before giving my own general view on the matter of the pre- 
ceding paragraphs, the following passage from a letter of F. W. 
Robertson, 2 who is listed in the day-night group above, will be of 
some interest. "Midday is like mid-life — full of commonplace, of 
toil and with less of romance. . . . Morning and evening correspond 
with youth and age, in both of which there is a peculiar poetry. . . . 
Heaven lies around us in our infancy, and I suppose the mystery of 
the grave brings heaven again around our decadence, just as the sun 
approaches the horizon again at evening." He thinks the wonder 
and mystery may seem lacking at midday because the sun is directly 

1 For very many years (30-50), so it is said, the villager of Konigsberg was 
wont to set his watch by the unvarying appearance of Kant for his daily walk. 
Whether the latter's production could have been so well sustained without this 
regularity one is inclined in his case to answer in the negative. Chalmers was 
another shining illustration of the methodical worker. It is said that " so far 
before him could he see, and so methodically did he proceed, that he could 
calculate for weeks and months beforehand the rate of his progress and the 
day when each separate composition would be finished." " His taste for 
numerical arrangement was exhibited in the most insignificant actions and 
habits of his life. It regulated every part of his toilet — down even to the daily 
stropping of his razor. ... He did almost everything by numbers. His 
staff was put down regularly at every fourth footfall; and the number of its 
descents gave an accurate measure of the space over which he had walked. 
Habit had rendered count an easy, almost mechanical, operation; so that, 
though meeting friends, and sustaining animated conversation, it still went 
on." Among the imaginative authors, Anthony Trollope stands as the repre- 
sentative of composing by the watch, which he literally did. Says he : "I 
have always prepared a diary, divided into weeks, and carried it on for the 
time I have allowed myself for the work. In this I have entered day by day 
the number of pages written, so that if at any time I have slipped into idleness 
the record stares me in the face and demands increased labor." And this he 
does " whether other business is heavy or light, or whether the book is wanted 
with speed or not." . . . Much dispute arose as to the quality of Trollope's 
work, partly prejudiced by his thus violently flying into the face of ' inspira- 
tion,' but a just critic must grant that his novels are not lacking in real 
imaginative character. 

2 S. A. Brooke, Life and Letters of F. W. Robertson, 1: 341-342. 1865. 



66 DIURNAL COURSE OF EFFICIENCY 

above and unseen then, and seem more present at the other periods 
because it is more visible then. 

If we admit the fact of a noticeable tendency toward the selection 
of night for the creative types of composition, it seems to me that 
the underlying causes, as far as not concerned simply with the chance 
distribution of individual differences that obtains in all human 
activities, are more extensive than either of the foregoing explana- 
tions implies. Not only ' physical fatigue' — often exhibited in 'high- 
strung' persons as nervous excitation, as well as 'luxurious repose' 
in others — and mysterious solar influences, appear as factors, but 
the greater quiet and darkness and the heavenly phenomena — all with 
their indefinable associations, the prevailing social customs, and the 
use of artificial stimulants, should not be overlooked. 

The first of this last set of causes needs no lengthy discussion. 
We are all probably more affected by such associations than we our- 
selves are consciously aware. Such influences as are apt to affect 
impressionable temperaments at that time are most admirably sug- 
gested by the following extract from Cable, giving the local and 
temporal setting of his novel, 'Madame Delphine': "A beautiful 
summer night, when all nature seemed hushed in ecstasy, one of those 
Southern nights under whose spell all the sterner energies of the 
mind cloak themselves and lie down in bivouac, and the fancy and 
the imagination, that can not sleep, slip their fetter and escape, 
beckoned away from behind every flowering bush and sweet-smelling 
tree, and every stretch of lonely, half-lighted walk, by the genius 
of poetry." 

The second and third causes bring me to the expression of the 
general thesis, which is only this : that excitation of some sort is most 
often the precondition of the highest imaginative work. That one's 
wits — to speak popularly — are sharpened by either enlightening or 
enlivening conversation, and that immediately subsequent pen-work 
is rendered correspondingly easier, will scarcely be disputed, if indi- 
vidual cases of over-excitement be excluded. 

And that the prevailing social customs have much favored this 
sort of excitation may be inferred from remarks of the following 
tenor. John Wilson 1 : " In Dumfries, as in every other considerable 
town in Scotland— and we might add in England— it was then cus- 
tomary, you know, with the respectable inhabitants, to pass a con- 
vivial hour or two of an evening in some decent tavern or other. . . . 
The worthy townsfolk did not frequent bar or parlor or club-room 
— at least they did not think they did — from a desire for drink, 
though they doubtless took a glass more than they intended, nay, 

1 Genius and Character of Robert Burns, 161. 1861. 



COURSE OF MENTAL EFFICIENCY 67 

sometimes even two ; and the prevalence of such a system of social 
life, for it was no less, must have given rise, with others besides the 
predisposed, to very hurtful habits. They met to expatiate and 
confer on state affairs, to read the newspapers, to talk a little 
scandal, and so forth, and the net result was, we have been told, con- 
siderable dissipation." A number of citations of individual cases, 
in confirmation of the wide occurrence of this custom, could be as- 
sembled, if space permitted. 1 

Even less mention can be made, or special illustration given, of 
the other numerous and well-patronized methods of mental stimula- 
tion — from ordinary walking, riding or music to hourly service of 
blackest coffee, greenest tea or strongest opium, or to constant use 
of tobacco, before and during composition. The extensiveness of 
this among the imaginative writers is striking. While these customs, 
or even the most radical of them, are not confined to the night con- 
tingent of the army of the quill, they are most notably represented 
there. Perhaps a very slight basis of this may lie in the fact that, 
if one felt some social odium or attribution of weakness might attach 
to over-indulgence in these directions, it would be easier and more 
politic to maintain them at night than at any other time. This would 
also be favored by the closely succeeding chance of 'sleeping off' ill 
effects that might otherwise be distressing. 

The data here are not voluminous nor reliable enough to make 
possible any scientific determination of the extent to which the vari- 
ous factors are individually involved in the apparent special prefer- 
ence for night-time by imaginative writers, and how far it is a purely 
instinctive inclination. The information necessary to the solution 
of this may some time be at hand, but at present we are only in pos- 

1 Extempore rhyming, once so popular in parts of Italy, in reference to our 
problem has bearing on both evening composition and external excitation. 
This description — much shortened — is to be found in Spenee's Observations, 
Anecdotes and Characters, pp. 248-251: "The improviso . . . poets in 
Italy are actually what they are called . . . and do it Avith great emulation 
and warmth, generally in octaves, in which the answerer is obliged to form 
his octave to the concluding line of the challenger; so that all the octaves 
after the first must be extempore, unless they act in concert together. Our 
method is to create our thought at the enemy's seventh verse : then we have the 
idea, the rhymes, the words and the verse to think of, only while our opponent 
i3 repeating his last line, which we take no manner of notice of at all. We 
almost always do better the second half hour than the first, because one grows 
warmer and warmer, to such a degree at last that, when I have improvised all 
evening, I can never get a wink of sleep all the night after. . . . Cavalier 
Perfetti, of Sienna, the best in Italy at present, ... is so impetuous in 
improvising that sometimes he will not give way for the guitar " ( Signor 
Nanechi) . 



68 DIURNAL COURSE OF EFFICIENCY 

session of the practical fact that many writers do actually prefer, 
use. and do their best work in, the night hours. 

A noteAvorthy exception to this fact is found in the case of the fe- 
male authors, indicated in the above lists by F. In all there are 18, 
distributed as follows: 10, morning; 1, afternoon; 2, night; 2, morn- 
ing-afternoon ; 3, whole day. Remembering that the last five belong 
partly in the first group, and that the night groups have slight rep- 
resentation, it will be seen that the early hours of the day are de- 
cidedly in the ascendency as to preference. This is quite in harmony 
with what has preceded, in this paper, regarding the peculiarities of 
the female diurnal curve. 

Many individual incidents, of intrinsic interest and of some scien- 
tific value, must be omitted; but two short instances of what is re- 
ferred to may be transcribed. T. J. Hogg, 1 reports of Shelley that 
"at 6 p.m. he would suddenly compose himself, even in the midst of 
a most animated narrative or of earnest discussion ; and he would lie 
buried in entire forgetfulness, in a sweet and mighty oblivion, until 
10, when he would suddenly start up, and rubbing his eyes with great 
violence, and passing his fingers swiftly through his long hair, would 
enter at once into a vehement argument, or begin to recite verses . . . 
with a rapidity and an energy that were often quite painful." Sir 
Walter Scott 2 was furnished by Comte de Tressan with this descrip- 
tion of the late days of A. R. Le Sage, the noted French novelist: 
"Mons. Le Sage, awakening every morning as soon as the sun ap- 
peared some degrees above the horizon, became animated, acquired 
feeling and force in proportion as that planet approached the 
meridian ; but as the sun began to decline, the sensibility of the old 
man, the light of his intellect, and the activity of his bodily organs, 
began to diminish in proportion ; and no sooner had the sun de- 
scended some degrees below the horizon, than he sunk into a lethargy, 
from which it was difficult to arouse him." This, if true, is cer- 
tainly a remarkable instance of diurnal rhythm. 

This must close our account with the authors. On the whole, it 
appears that they elect the hours most frequently used by students 
for their study. 3 It is possible that we have here suggested, not the 
most 'ideal' program, but the most practical one. For those who 

1 Quoted by E. T. Mason in Personal Traits of British Authors, 1: 110. 
1885. 

2 Lives of Eminent Novelists and Dramatists, 596. Undated. 

3 It was said above that some writers were included whose actual working 
hours were used, in lieu of a distinctive preference. By far the larger part of 
these occur in the two longest day groups, and especially in the whole-day group. 
The percentage of the latter group is thus too high and the others — particularly 
morning and night, as judged from known cases — are correspondingly too low. 



COURSE OF MENTAL EFFICIENCY 69 

can not stand a sixteen-hour stretch, it may be better to put the 
relaxative period as an interlude rather than as a postlude. Pro- 
ductively, whether a period of relaxation in the midst of the day's 
work is good or bad depends on the individual make-up and can not 
be judged aside from that; but the 'productive' standpoint is the 
best one to take, if it be true that ' we live in deeds and not in years. ' 
Productively, if not indeed constitutionally also, too much rest is as 
injurious as too much work. The fact is frequently overlooked that 
much rest, habitually indulged in, tends to beget a more-rest disposi- 
tion, just as, so the economic moralists tell us, a person's needs are 
likely to increase with his wealth. It is important to remember that 
the psychological phenomenon of practise effect acts in rest and 
work in general just as it does in the particular manifestations we 
have been dealing with above. In either instance, a limiting level of 
productivity is eventually reached. In most lives these matters are 
left to regulate themselves, without a great amount of conscious or 
systematic direction. We make ourselves believe that this is always 
due to external conditions, but we have examples, several of which 
were mentioned above, of lives successfully ordered by intelligent 
choice. The poetic temperament is peculiar and such regularity 
would be unusual and possibly disastrous in many cases, but with all 
persons it is probable that more thought and self-experimentation 
along this line would result beneficially. 

No other pertinent work on the diurnal course of mental efficiency 
has been found save that to be cited under ' fatigue. ' The testing of 
such mental complexes as have been referred to is deemed impor- 
tant in proportion to the homogeneity of the tested group, and the 
preceding discussion has been limited for the most part to persons 
possessing considerable intellectual culture. Psychologically it would 
be valuable if tests were devised which would place on a comparable 
basis the mental operations of classes widely variant. This might 
lead to some fundamental knowledge as to the existence or non- 
existence of certain general or essential forms of mental process, and 
of their kinds, degrees, relations, etc., in any given activity. 



III. Brief Summary 

It is clear that whatever conclusions are made, respecting the 
data in this section, will be less firm than those of the one preceding. 
Still, there are some definite indications. As to the simpler mental 
functions first mentioned, one would infer that those which in their 
testing involve the use of motor elements tend to follow in speed the 
motor type of midday maximum, though making it a little earlier, 



70 DIURNAL COURSE OF EFFICIENCY 

while in accuracy the morning is favored, though but slightly. In 
the more strictly mental and in the more complex activities, there is 
a similar inclination to the morning periods both in rate and in accu- 
racy. Adult students and authors seem to think the earlier part of 
the day best for their respective employments, but in practise both 
draw heavily on the night period, while in the case of females and 
children the morning maximum seems to be the rule. The suggested 
morning efficiency of adults does not hold good, however, of the first 
moments after arising, where there still appears an inertness com- 
parable to that on the motor side, though less evident and more 
evanescent. 



NOTE 

There came to my attention as this paper was about to issue from the 
press, the interesting work of J. A. Bergstrom on ' A Study of Mental Activity,' 
in the Amer. Jour, of Psych, for 1894. Only chief and brief cross-references can 
be made. For rate of movement, a simple test was used; for old associations, 
classification of words, and the reading, adding and multiplication of numbers; 
for new associations, learning number series and nonsense syllables and the sort- 
ing of cards. 

In movement, J. A. B. made this record, in number of strokes per minute, — 
7 A.M., 262; 8, 272; 10, 278; 12, 267; 2 P.M., 277; 4, 270; 6, 269; 8, 260; 10, 
260 (p. 258). A subject of Mosso's made this record at 8, 10 and 12 A.M., — 260, 
268, 268 (p. 261 — cf. p. 17 above). 

In memory of nonsense syllables, E. C. S. progressively loses ability during 
the day ( p. 249 ) ; while J. A. B. is best at 8 A.M., and worst at noon and 6 P.M. 
(p. 256). In old associations (sorting cards), 3 subjects diminish in ability 
from morning to night, 1 increases, 1 is best in afternoon and worst at night 
and 1 is the opposite (p. 249) ; J. A. B. tends to follow his movement course, 
but the maximum is at 6 P.M (p. 258). For the other associational tests, 
J. B. A. found a uniform curve: low ability at 8 A.M., increasing to 10, decreas- 
ing to 12, increasing to 2 (same as 10), then a slight decline to 6 p.m. (p. 256 
— cf. p. 53). 

Some of his more general conclusions follow. 

No necessary correspondence between pulse and mental rate (p. 260). 

" Heerwagen sent out the following : What part of the day do you find 
mental work easiest? 182 said the morning, 133 the evening, 6 the afternoon, 
43 noticed no difference, while 28 found it easy at all times. Professor E. 
Barnes, in a study of the intellectual habits of Cornell students, received in 
reply to the same question, 66 votes for morning, 6 for afternoon and 39 for 
evening. The average student, he says, begins work at 8, but is in doubtful con- 
dition, is best at 9 and at 10 is still in good condition, at 11 is tired, and is at 
his worst at 12. He works from 3 to 5 p.m., but in inferior form; after supper, 
he goes to work at 7 and reaches his best at 8; from 9 he is not at his best, 
and retires at 10:30" (p. 262— cf. p. 59). 

" The familiar ' warming up ' to work is probably to be explained in large 
part by these facts of nervous activity ' ( summation phenomena ) . Fere - notes 
that reaction time does not reach its greatest rapidity till the stimulating in- 
fluence of light and heat has operated for some time. Nocturnal paralysis and 
morning tire are explained as exaggerated phenomena of this sort' (p. 264 — 
cf. p. 71). 

"The daily mental rhythm is much influenced by habit (p. 266 — cf. p. 74). 
These habits ( of authors ) , however acquired, evidently have great power of dis- 
tracting the attention if they are not satisfied, and so retard work " (p. 267 — cf. 
p. 76). 

No apparent effect of fatigue upon sensory discrimination (p. 266 — cf. 
p. 79). 

" Stimulations which would inhibit in normal conditions, in fatigue produce 
reinforcement. The fact that reinforcements of sensations and muscular move- 
ments are more prominent in neurasthenic and hysterical persons seems to be 
paralleled here. The greater excitability and sleeplessness in fatigue are an- 
other illustration" (p. 263 — cf. p. 88). 

" There is no general type of daily rhythm, and individual differences of 
the most striking sort occur " ( p. 262— -cf. p. 95 ) . 

These results and conclusions largely agree with my own. 



D. CHIEF CAUSAL FACTORS IN THE DIURNAL 
EFFICIENCY CURVE 

The main effort up to this point has been to bring together the 
data that appear to have most direct bearing on the question of 
diurnal rhythms. It is only after such an assemblage of the facts 
that a discussion of the causal factors can profitably be begun. The 
problem is of such nature that it could utilize every known psy- 
chological fact, on the one side, and run into every possible theory, 
on the other, if its utmost reaches were sought. Yet, there is no ulti- 
mate satisfaction in a purely factual description, correct to the last 
word — there is always the demand for explanation, or deeper facts. 
It is to an endeavor to meet this demand in some degree that the 
present section is mainly devoted. 

I. Night-Day Rhythm— Sleep and Activity 

A first approach to a solution is made when it is intimated that 
the day-night process exhibited by nature is the primary condition 
upon which depends the daily broad human rhythm of sleep and 
activity. The wakeful period is the only one that has hitherto been 
touched in this paper, but the variations occurring therein can not 
be explained without reverting to the preceding period of inactivity. 

Donaldson 1 gives this physiological explanation of the whole mat- 
ter: "After recuperative sleep the cells in the nervous system are 
full-sized and granular, blood flows with a medium pressure through 
the nerve centers; slight stimuli elicit a ready response and there 
are general sensations of well-being and vigor. From the beginning 
of the day the process of running down goes on ; all the constant 
stimuli hasten it, meals retard it, drugs modify it, per their nature. ' ' 
The night inactivity is due to accumulation of waste products of the 
day's activity, and sleep to cerebral anemia caused by withdrawal 
of the blood from the brain at this period. He thus makes one fun- 
damental, long rhythm — a gradual depression toward night and 
recuperation by sleep. 

All sorts of things have been asserted about the office of sleep in 
the human economy, 2 and it is obvious that it plays a highly bene- 
ficial part. Theoretically, Donaldson's view is most credible, but 
experimentally it proves untenable as a general expression of the 

1 Growth of the Brain, 322-323. 1898. 

2 For the most peculiar, see Bigelow, The Mystery of Sleep. 1895. 

71 



72 DIURNAL COURSE OF EFFICIENCY 

facts. Adults are probably not at their best on arising and fre- 
quently show highest abilities in the evening. Aside from possible 
histological evidence in its favor, the strength of the opinion that 
early-morning efficiency is highest seems due to the failure to apply 
exact measurements, leaving judgment to the feelings, which are 
confessedly unreliable. One can not tell just how much he is doing by 
the effort he seems to be expending, as various sorts of delusional and 
reinforcement effects show. The early morning may be accompanied 
by a not unpleasant ennui, like that of a convalescent, which would 
not at all suggest the idea of inefficiency, while the afternoon is often 
accompanied, for many, by positively disagreeable feelings of weari- 
ness, which emphatically lead to the idea of simultaneous inefficiency. 
Inefficiency results from weariness, but the amount tends to be over- 
estimated in our minds while the inefficiency of the morning tends 
to be relatively underestimated. 

The presence of inefficiency after sleep is shown not only in the 
foregoing pages, but was also found by Roemer, 1 experimenting on 
this matter directly. He sought to determine psychic efficiency (1) 
after normal sleep and (2) after curtailment of the normal period of 
sleep at the morning and night ends. His tests were memory of 
figures, addition, controlled reaction-time and association. His re- 
sults are not given tabularly but stated thus : 

(a) The condition shortly after arising from normal sleep is one 
of more or less weariness (MiidigJceit) . 

(&) Cut off sleep at the night end, and little alteration occurs be- 
cause the loss is made up by deeper subsequent sleep. 

(c) Cut off sleep at the morning end, and fatigue (Ermudung) 
results. 

Later 2 he essayed to ascertain the effect of afternoon sleep on 
performance and found— by tests of memory and addition — that a 
male, 'normally feeling languid after lunch,' showed marked increase 
of ability after a nap; while a female, not subject to such languor, 
showed the opposite effect. . 

From these experiments he concludes that Mudigkeit is a brain 
condition, while Ermudung is due to tissue consumption in the organ- 
ism. As the connotation of 'fatigue' has been narrowed since 'weari- 
ness' has received acceptation, so it should be still further restricted 
by another characterization representing this morning condition, 
which may well be termed ' inertness. ' This carried-over sleep effect 

1 ' Ueber einige Beziehungen zwischen Sehlaf und geistigen Thatigkeiten,' 
Vortrag, Cong, fur Psych. 1896. 

2 ' Experimental Studien iiber den TSTachmittagsschlaf,' Allgetn. Zeitschrift 
f. Psychiat., 53: 860-863. 1897. 



CAUSAL FACTORS IN DIURNAL EFFICIENCY CURVE 



73 



seems something different from the weariness and fatigue that result 
from the day's activity. This matter will be taken up again soon. 
In respect to Roemer's second investigation, regarding afternoon 
sleep, the alleviation of the condition of fatigue in one subject, and 
the initiation of inertness in the other, may be sufficient to explain 
the results. 

Various researches on sleep have established the fact that by far 
the soundest portion during the night is that of the first three hours. 
For instance, this was found by Michelson 1 to be true for four sub- 
jects. The writer has chosen from his plotted curves one which 
would be more typical of their average tendency, if it reached a 
maximum at the second hour instead of the first ; but it was selected 
rather with a view to illustrating a conception of how early morning 
inefficiency arises and how the start of the fundamental diurnal curve 
is determined. 






m 






AM. 










P.M. 






i \ < 


7 1 


1 ' 1 ? : 7 


















.-*'" 


""---. 


-^ 
























■** 


' — 


-5 

-10 
-15 
-20 
-it 































































































































Fig. 5. The Hourly Depth of Sleep — after Michelson. 

If this curve of degree of unconsciousness be conceived as repre- 
senting a person's degree of physical inefficiency, it will be noted 
that normal ability, designated by the base line, is not reached on 
arising, but that the curve is slowly approaching it at this point and 
at the same general rate would reach it about 10 or 11 a.m. The facts 
already cited lead us to suppose that this is exactly what happens. 
Sleep imposes an inertness, more or less pronounced, whose influence 
but gradually passes away in adults on arising. This first condi- 
tion represents, as it were, an adaptation of the organism to nocturnal 

1 ' Ueber die Tiefe des Schlafes,' Psych. Arbeiten, 2 : 1 Heft. 



74 DIURNAL COURSE OF EFFICIENCY 

inactivity, to remove which some little time is required after awaken- 
ing to the exigencies of active life. 

As the period prior to awakening can be thought of as one of 
dwindling negative internal stimulation — of passing sleep effect — 
so may the subsequent period be considered as one of increasing posi- 
tive auto-stimulation — of growing awakeness. It would not follow 
— though it would be suggested — that because sleep exhibits different 
levels of consciousness, therefore wakeful life should do the same, but 
the fact is experienced by all and needs no proof. The inner tend- 
ency to 'warming up,' due partly to habit, is amplified by the cumu- 
lative effect that succeeding stimuli have on us — an effect which is 
seen in its simplest and most definite form in the well-established 
fact of 'summation of stimuli,' demonstrated by physiological ex- 
periments on muscle and nerve. The physiological discharges take 
place more and more readily during the morning, till a certain level 
is reached for the individual, or accidental causes of depression inter- 
fere. In short, it may be said that the night's general habit of in- 
activity and the night's immediate sleep effect are instrumental in 
imposing on us a morning period of physical inertness, more or less 
reflected in the mental life ; and that the general habit of day activity 
together with its frequently repeated stimulations tends increasingly 
to lead us to higher levels of efficiency — up to a certain limit. 

This tendency meets with modifying and restricting influences, 
however, the relative force of which determines the actual form of 
the efficiency curve for each individual. "When one reviews some 
of the things which can profoundly affect the human organism in its 
functionings, the first thought is that there could be no great part 
of the individuals in any group who would probably conform to any 
one type of curve. This seems to be true when any great refinement 
of it is undertaken. But in the broad sweeps suggested, there is still 
chance of coming to ground common to many, as was shown in the 
previous paragraph. Personal habits are accidental as far as a 
common curve is concerned, and must therefore be disturbing ele- 
ments. They can not profitably be treated apart from the actual 
cases, save in a general way, but the universal custom of eating offers 
something more substantial for discussion. 

II. Habits, Meals, etc. 

The effect of habit was used as a partial basis for the preceding 
statements. It is also applicable when the habit is more special and 
is voluntarily assumed. If a person, with afternoon maximum 
strength, were consistently and long to exercise only in the morning, 



CAUSAL FACTORS IN DIURNAL EFFICIENCY CURVE 



75 



his curve would very probably be altered accordingly. Students are 
proportionately much, better at night in mental labor than people 
unaccustomed to study then. Writers who have set the morning as 
the time for composition in spite of feelings to the contrary, come 
eventually to consider it their best period and work then with the 
least friction. Illustrations might be multiplied, but it seems enough 
to say that, in general, just as physiologically there occur periodic 
hints of meal-time— even to the point of faintness and sickness with 
some people, if the customary time be passed by so much as an hour 
— so it is probable that in all cases of habituation similar phenomena 
occur which, with their mental accompaniments, become the sources 
of secondary fluctuations in the individual curves. 

"The noonday dinner gives one both a bad stomach and a bad 
conscience, and results eventually in an empty head." So says 
O'Shea, 1 after much attention to the food question in relation to 
mental economy. Roemer 2 experimented eight days on the effect of 
food, using as tests half hours of addition at 9, 10, 11 a.m. and 12 m. — 
four days with breakfast and four days without, alternately. Table 
XXIX. shows, first, the absolute number of additions and, second, 
the reduction of the same to percentage of the first hour's per- 
formance. 

Table XXIX. Effect of Loss of Meals on Adding Ability — After Roemee. 



Number added. 

Per cent, of first hour. 



Without food. 
9 A.M. 10:00. 11:00. 12:00. 



6,741 5,856 5,707 5,990 
100 87 84 90 



With food. 
9 A.M. 10:00. 11:00. 12:00. 



i 8,695 8,453 7,906 7,831 
100 97 91 89.5 



The series of experiments was too short to prove anything, but 
the results, in the light of the noon records, scarcely seem to suggest 
his conclusion of a beneficial food influence so much as that the rela- 
tively bad records at 10 and 11, of the days without food, were 
dependent on the disturbance consequent upon the irregularity. It 
is but fair to Roemer to say that he admits this as a possible factor, 
but he fails to give it sufficient weight. 

Kraepelin 3 holds a similar view as to food effect: "The psychic 
disposition of the individual shows in general during the day quite 
definite changes — an increase of performance ability till about noon, 
a quick fall after lunch, a new increase in late afternoon and a final 

1 Op. dt. 

2 Weggandt, ' Roemer's Versuehe iiber Nahrungsaufnahme u. geistige Leist- 
ungsfahigkeit,' Psych. Arbeiten, 2: 695-706. 1899. 

3 ' Ueber Ermiidungsmessungen,' Archiv f. die gesamte Psych., 1: 9-30. 
1903. 



76 DIURNAL COURSE OF EFFICIENCY 

evening fatigue. Regeneration is accomplished by food on the one 
hand and by sleep on the other." He later alters this; namely, he 
finds an increase, both physical and mental, after each meal. This 
is the source to him of the diurnal variations. 

That meals have an influence is true, but that it consists in an 
immediate tendency to increasing ability is not clearly seen. Finzi, 1 
for one, says just the opposite — that they reduce the speed of all 
functions. Many, if not most, experimenters on the effects of dif- 
ferent agencies (alcohol, tobacco, food and foodstuffs, drugs, sleep, 
etc.) fall into what seems to be a serious error, already mentioned. 
That is, the fact is overlooked that elimination of customary influ- 
ences affects the organism as radically as does its subjection to posi- 
tive stimuli. The immediate effect of breaking a habit is apt to be 
detrimental, whatever the habit may be. This, it may be said in 
passing, is one of the most subtle— and vitiating— elements of all 
experimentation. When a smoker quits that habit for a few experi- 
ments, two causes figure in the result ; one the change of a particular 
condition— which is the one aimed at— and one the alteration of an 
habitual condition — which is the one so frequently ignored. There 
is reaction to the one as to the other, physiologically and psycholog- 
ically. The writer found in a five days' course of fasting, by both 
objective tests and subjective feelings, that the greatest disturb- 
ance, mentally and physically, occurred on the first and second days 
—the latter particularly— after which gnawings, headaches and 
nausea began noticeably to subside and the abnormal condition 
tended appreciably to become normal to the end of the course. Data 
obtained only from those first few days would have been quite mis- 
leading. 

Some good evidence on the persistence of habitual periodicity in 
activity is contained in an article by Patrick and Gilbert on the 
'Effect of the Loss of Sleep,' 2 though the authors do not utilize the 
material for this purpose. Two subjects, A. G. S. and G. N. B., were 
kept awake 72 hours and various tests were given them every 6 hours. 
On successive days, the worst records were made at the following 
hours, showing the subjective disturbance to be greatest at the periods 
ordinarily devoted to inactivity— to sleep. The first day, being un- 
affected, is omitted. 

1. Adding. 

A. G. S.— 3 a.m., 3 a.m., 9 p.m. (last test taken). 
E. N. B.— 3 a.m., 3 a.m., 9 p.m. (last). 

1 Normalen SchicanJcungen der Seelenthatigkeiten, Reprint, p. 14. 1900. 

2 Univ. of Iowa Studies in Psych., 1: 40-61. 1897. 



CAUSAL FACTORS IN DIURNAL EFFICIENCY CURVE 77 

2. Hearing. 

A. G. S.— 3 a.m., 3 a.m. (none after 3 p.m.). 
E. N. B.— 3 a.m., 9 p.m., 3 p.m. and 9 p.m. (last). 

3. Discrimination of letters. 

A. G. S.— 3 a.m., 3 a.m., 3 a.m. and 9 p.m. (last). 

E. N. B.— 3 a.m. and 9 p.m. to 9 a.m., 9 p.m. to 9 a.m. and 9 p.m. 

4. Strength. 

A. G. S.— 3 a.m., 3 a.m., 9 a.m. (none taken at 3 a.m.). 
E. N. B.— 3 p.m., 9 a.m., 9 p.m. (last). 

5. Memory. 

A. G. S.— 3 a.m., 3 a.m. and 9 p.m. to 3 a.m., 9 p.m. (last). 
E. N. B.— 3 a.m. and 9 p.m., 3 p.m., 9 p.m. (last). 

The times of the best records point just as strongly in the same 
direction. These results, aside from the effects of loss of sleep, show 
the recurrent nature of an established habit and how important 
must be its influence in every individual curve. 

By all my subjects, the heaviest meal of the day was eaten about 
6 or 7 p.m. ; hence the fourth period should show the best work, if 
meals alone cause the differences. Subjects I. and A ate very light 
lunches, yet the 5 p.m. period is the best, as to strength at least. 
Lombard 1 seems to be right when he says, "the temporary influence 
caused by a meal can not long delay the decline nor can it hasten 
the increase of strength which is caused by the diurnal alterations 
of the power." Rest and social elements are also involved in the 
nature, amount and permanence of the change in ability wrought 
by the meal interval. 

III. Fatigue and Feelings op Fatigue 

Granted that periodical changes in individual curves of efficiency 
do exist for time of day, it is evident that no credible theory of their 
cause could be constructed without reference to those effects, to 
which all are subject, that have been treated usually under the head 
of ' fatigue. ' 

Chronologically, the study of diurnal variations in ability orig- 
inated from an interest in the problem of fatigue. One can not look 
over the literature of the subject without noting that the experi- 
ments on motor power, following the introduction of the Mosso ergo- 
graph in 1890, were largely influential in turning attention to the 
measurement of human functions, mental even more than physical. 
Some earlier work had been done by Sikorsky ('79), Hodge ('87), 

1 ' Some Influences affecting Voluntary Work,' op. cit., p. 30. 
6 



78 DIURNAL COURSE OF EFFICIENCY 

Galton ('88), Oehrn ('89), and a few others, but did not attract 
much attention. In Germany, an immense impetus was given to 
such investigations by pedagogical needs and, indeed, the whole prob- 
lem of periodicity and fatigue may be said to have taken its rise 
from this relation to school life, and its solution to have its most 
valuable application there. Therefore the treatment of this section 
will be rather extensive, though it will be impracticable even to refer 
to the mass of original work in this direction undertaken since 1890. 

1. Muscular Fatigue 
Fatigue tests here are, in one aspect, strength tests, and, there- 
fore, have already received some mention. By far the greater 
amount of the work in this immediate connection has been taken 
up with a view to determining the location of the seat of fatigue 
— whether it is central, neural, muscular, etc. Ultimately these 
considerations must be utilized in any thoroughgoing treatment 
of the diurnal problem, but the same can as truthfully be said 
of any group of facts concerning the living being, if the question 
be in no wise limited. So far, then, as these experiments have 
been carried out without reference to time of day they must be 
ruled out, but so far as they have been used as mental measures, 
they will be discussed immediately below. 

2. Mental Fatigue 

1. Measured by Motor Inefficiency. — One primary question, 
whether decrease in muscular power is a trustworthy sign of 
fatigue in mental function or not, has sometimes received em- 
pirical consideration, but quite as often an affirmative answer has 
been assumed as true. 

Bolton, 1 in the course of his theory of motor development, 
says: "Tests of motor power may be used as measurements of in- 
telligence or mental alertness. ... As substitutes for the old- 
fashioned methods of examination . . . tests of physical en- 
dowment and of general healthfulness of body seem to offer the 
most promise. . . ." 

Lukens 2 is authority for the statement that Kemsies with the 
ergometer found distinct correlation between mental fatigue and 
lessened muscular power and that 'the ergometer showed the 
fatigue in certain cases to have continued several days' after 
some insevere night mental tests. 3 What he found the following 

1C Motor Power,' Am. Jour, of Psych., 14: 615-631. 1903. 

- ' The School Fatigue Question in Germany,' Ed. Rev., 15. 1898. 

s Bettman (see Bibliog., Part E) also says that, though no permanent 
injury to ability resulted from night tests in adding, ' a very strong fatigue 
affected the disposition for several days following.' 



CAUSAL FACT0R8 IN DIURNAL EFFICIENCY CURVE 79 

mornings was probably not residual fatigue so much as the nor- 
mal condition of inertness. He and others have arranged cur- 
ricula in accordance with the results of such ergographic tests 
after recitations in the various branches. 

Christopher and Smedley, in the articles noted above, make 
the assumption of such a direct relation between mental fatigue 
and motor force, the former advising that 'physical condition 
should be a factor in grading, especially for entrance to first 
grade,' while Smedley says that 'certain parts of the school day, 
when pupils on the average have a higher storage of energy than 
at others, should be utilized for the highest forms of educational 
work.' The one assumes that mental fatigue is present when 
the ergographic records are low; the other, that it is absent when 
they are high. 

Ellis and Shipe 1 assume throughout their trials that fatigue 
is present in the afternoon, and hence when the tests fail to show 
it, the tests are voted valueless. They took reaction-time and 
ergographic tests on six subjects for five days, twice a day ( 1 
a.m. and 12:30 p.m.) and found that "these tests seem to show 
that the students (college) were as fresh at noon as at the be- 
ginning of the day. Their appearance and feelings belied their 
results" (p. 234). Such acceptance of the emotional evidence 
of fatigue is an easy but serious mistake to make. Various 
writers 2 have pointed out the need of observing the distinction 
between fatigue proper and the feelings of fatigue. 

Where my own subjects noted mental depression or even head- 
ache on their records, the figures rarely failed to show a high 
grade of muscular performance at the time. But the younger 
the individual the more prone he is to follow his feelings, in the 
quantity and quality of his work. Especially was this noticeable 
among the coin-case workers, whose every (seen) gape and sleepy 
look was duly registered. Still, it is yet to be proven that there 
is a causal connection between mental and motor deficiency such 
that one may be an accurate measure of the other. 

2. Measured by Sensory Inefficiency. — Another conception is that 
the degree of insensitivity of the skin is a measure of fatigue. 
Griesbach- 3 was the originator of the esthesiometric method of study- 
ing fatigue and performed many experiments with it. He deter- 
mines the least distance on the skin at which the two points of the 

* 'A Study of the Accuracy of Present Methods of Testing Fatigue,' Am. 
■Jour, of Psych., 14: 232-245. 1903. 

» Cowles, MacDougall, Dearborn, Thorndike, Kraepelin, Roemer, etc. 

» Energetik und Hygiene des Nervensy stems in der Schule, S. 1-95. 1895. 



80 DIURNAL COURSE OF EFFICIENCY 

instrument, on being gradually approached from a point where they 
are easily distinguished, are perceived as two; or the greatest dis- 
tance at which two points are perceived as one, on being gradually 
separated, from below the so-called threshold. His results were 
thought remarkably decisive and consistent, so much so that, like 
his followers Vannod and Wagner with the same instrument, and like 
Kemsies and others with the ergograph, he was able to obtain a 
fatigue coefficient for each branch of study and then to assign each 
to its proper place in the daily school routine. The only trouble is 
that the different results do not accord. 

Griesbach found that the sensitivity changes little during the 
day under normal conditions, but gradually decreases under school 
conditions. He tested the pupils, professors and mechanics of a 
school, on the forehead, nose, cheek, underlip, ball of thumb and ball 
of forefinger. By averaging these six determinations he obtained 
a very typical curve of the changes in the threshold. The following 
figures show the resulting values in millimeters. 

Table XXX. Esthesiometer Tests — Revision aftee Geiesbach. 















a 
















•4 




8 

< 


a 


A.M. 

reek. 


< 


© 
"So 


•< 


>* 


a ta 




tS 


P.M. 

est. 


S M lA 


*~ 


y 


00 


h) 


a> & 


~ 


M 


i-l 


Ph 


s « 


- 1 


M 


« « 


2 fcO 


5.8 


1 


8.0 


| 


10.0 


10.8 


| 


7.3 


1 


9.8 


— 


| 


3.5 


2.7 



Griesbach, therefore, demands (1) no school work in the after- 
noon, (2) later beginning in morning— on account of residual fatigue 
from the previous day, (3) abolishment of examinations, (4) less 
home work and less learning by heart. Special attention is called 
to the high afternoon sensitivity compared with that of the early 
morning — true both of the work-day and the rest-day following. 
His method has been much tried and criticized, but only a few of 
the leading articles can be referred to. 

MacDougall, 1 after adverse criticism of other methods, says of 
Griesbach 's that it is 'decidedly satisfactory'; that by it can be 
found the best hours and days for study and the length of study 
periods proper for different ages. He produces no experimental 
proof of his own. 

Leuba 2 attacks the method and results. He tested three adult 
male students for fourteen days, at 9 a.m., 11 a.m., 1 p.m., 5 p.m. and 
9 p.m., on cheek and thumb, 6,000 judgments in all. He found 

1 Am. Jour, of Physiol., 19. 1898. 

2 ' Validity of the Griesbach Method of Determining Fatigue,' Psych. Rev., 
6. 1899. 



CAUSAL FACTORS IN DIURNAL EFFICIENCY CURVE 



81 



divergent results as between cheek and thumb and as between one 
and two point determinations on the thumb alone, and his results 
were also diametrically opposed to those of Griesbach, Vannod and 
Wagner. They showed, on the whole, a marked increase in sensi- 
tivity up to 5 p.m. and thence a steady decrease. The results for 
this group and for the one described below are graphically repre- 
sented in his publication, but have been transmuted into figures by 
the present writer, as indicated in Table XXXI. Work and rest 
days are given separately. The second series was on six adult 
female students, 2,000 judgments, at 8 :15 a.m., 10 :15 a.m., 11 :15 p.m. 
and 1:15 p.m. It gave similar results, diverse for forehead and 
cheek as to the single individuals, but showing considerable con- 
stancy in the total curves. The females also start with a relatively 
low sensitivity and increase as steadily as the males. 



Table XXXI. 



esthesiometek tests: threshold in mm. revision after 

Lettba. 



Male 


9:00 A.M. 


11:00 A.M. 


1:00 


P.M. 


5:00 


P.M. 


9:00 P.M. 


Subjects. 


Work. 


Rest. 


w. 


R. 


W. 


R. 


w. 


R. 


W. R. 


1 


14.5 


14.0 


15.1 


13.3 


14.5 


13.6 


14.0 


14.1 


14.4 14.6 


2 


15.8 


15.4 


15.2 


15.5 


15.7 


16.2 


14.9 


16.1 


14.8 16.6 


3 


8.0 


8.4 


7.5 


7.2 


7.4 


7.1 


7.1 


6.7 


8.1 7.6 


Average. 


12.8 


12.6 


12.6 


12.0 


12.5 


12.3 


12.0 


12.3 


12.4 12.9 


Female 


8 : 15 A.M. 


10:15 


A.M. 


11:15 


A.M. 


1:15 


P.M. 




Subjects. 


Forehead 


Cheek. 


F. 


C. 


F. 


C. 


F. 


c. 




1 


16 


22.0 


15 


22.0 


14 


20.5 


14 


20.5 




2 


11 


13.0 


9 


11.0 


11 


15.0 


10 


12.0 




3 


7 


11.0 


6 


11.5 


4 


8.0 


3 


8.8 




4 


12 


21.9 


17 


21.0 


14 


22.0 


13 


22.1 




5 


8 


10.0 


6 


8.8 


7 


8.0 


8 


8.0 




6 


8 


11.0 


5 


11.0 


5 


11.1 


5 


9.0 




Average. 


10.5 


14.8 


9.7 


14.2 


9.2 


14.1 


8.8 


13.4 





Germann 1 used both one and two points, noting the number of 
errors at the threshold. The experiments were made on an adult 
female student studying eight or nine hours daily; she was tested 
at about 8 :30 a.m. and 9 :30 p.m. ; 2,450 judgments were made. 
Table XXXI. gives the results of fourteen days, in each of which 
a pair of tests were taken. 



Table XXXII. 


ESTHESIOMETEB 


Records — After 


&ERMANN. 


Errors. 


A.M. = P.M. 


A.M. > P.M. 


A.M. < P.M. 


Total. 
2-point. 
1-point. 


4 
1 
2 


8 
9 
9 


2 
4 
3 



1 ' On the Invalidity of the Esthesiometric Method as a Measurement of 
Mental Fatigue/ Psych. Rev., 6. 1899. 



82 DIURNAL COURSE OF EFFICIENCY 

This means that the percentage of erroneous judgments in the 
morning was equal to that in the evening on four days ; greater on 
eight days; less on two days; etc. Hence he concludes that "in at 
least one normal case the percentage of errors in cutaneous tactile 
discrimination bears no constant nor even relative correspondence 
to the mental fatigue experienced by the subject." This conclusion 
is hasty, as it possibly confuses fatigue and feelings of fatigue and 
fails to take account of the state of inertia which has been emphasized 
as occurring early in the morning. 

It is suggested, therefore, that the morning insensitivity observed 
by these various experimenters is not at all a symptom of technical, 
nor of 'residual,' fatigue, nor yet of subjective weariness, but rather 
of inert physical condition unconnected directly with any one of 
them. It is also a mistake to assume that insensitivity can arise 
only as a result of fatigue, and just as much a mistake to suppose 
that much fatigue is necessarily present in adults in the afternoon 
or after several hours' effort. Many other authors also have demon- 
strated the unsafeness of this method for measuring mental fatigue. 1 

3. Measured by Mental Inefficiency.— A closer approach to a 
purely mental test of fatigue is found in the reaction-time or asso- 
ciation-time method first used by Cattell." In a course of experi- 
ments with different sorts of stimuli, reactions (1,950 in all) were 
continued for a whole day, from 7:30 a.m. to 8:30 p.m., with short 
intervals for eating. The results are thus summed up : " The first 
result to be noted is the very slight effects of fatigue ; in no case is 
the time lengthened more tban a couple of hundredths of a second 
and the mean variation is but little increased. We reach the un- 
expected conclusion that the processes which are most automatic- 
naming colors and simple reaction-time to sound— are the most 
affected by fatigue." 

This method was also employed by Roemer and by Ellis and 
Shipe. 3 The latter determined the reading time for words of four 
letters, in morning and at noon, and state their results in the words 
quoted on page 79, above. In regard to a second series of various 
tests, they say, "Of 24 perfect records reaction-time was shorter 
14 times at 5:30 p.m.; mean variation less 13 times; total figures 
added, more 17 times; more added correctly, 15 times; more cubes 
written, 19 times; more nonsense syllables learned, 15 times. One 
of the best records came just after a long, hard examination (in the 

*As Cattell, Ebbinghaus, Kraepelin ('99), Bolton, Meumann, Kraepelin 
('03). 

» 'The Time taken up by Cerebral Operations,' Mind, 12: 44. 1886. 
3 Op. cit. 



CAUSAL FACTORS IN DIURNAL EFFICIENCY CURVE 83 

afternoon) for which the student, after working and worrying all 
the day before had continued work till 2 a.m. the night before." 

Later, seven subjects were tested (1) during a week before March 
examinations, (2) during the examination week and (3) during the 
one following. The results practically agreed with those of previous 
series, and the authors report 'the same lack of agreement between 
tests and the same failure to indicate fatigue in the afternoon.' If 
they 'failed to indicate fatigue' they must have agreed somewhat, 
it would seem. 

Then three subjects were used (four, three and two days, re- 
spectively) at 9-10 a.m. and 5-6 p.m., and results were obtained 
'equally inconsistent with each other and with the undoubted facts.' 
These last citations show the assumption in the writers' minds that 
fatigue is the normal afternoon condition in the case of all adult 
students. 

It appears from their reports that the afternoon reactions and 
results in general were superior to those of the morning, even though 
the morning tests were taken rather late. Their series of experi- 
ments were short but, as far as they go, confirm the views expressed 
in the previous portions of this paper. 

One of the earliest tests to be used was that of 'dictation exer- 
cises,' introduced by Sikorsky in 1879— the first attempt at objective 
measurement of mental fatigue. It was later used by Oehrn ('89), 
Hopfner ( '94), Friedrich ( '96), and preferred to all others by Henri 
and Binet ( '98 ) . According to its advocates, it is easily given to 
groups, easily checked up, easy to understand, has no practise effect, 
and the different characters of the errors show the different types 
of fatigue (as for arithmetic, gymnastics, etc.). Only those of 
Sikorsky and Friedrich offer direct evidence on the problem in hand. 

Sikorsky, according to Binet, 1 gave 500 dictations to six classes, 
the members ranging in age from nine to sixteen years, at 9 a.m. and 
3 p.m., before and after the school session. The number of errors 
made by each class is given in the following table. 2 Binet classified 
these into phonetic (omissions and substitutions of letters), graphic 
(in written form, etc.), psychological (omissions or substitutions of 
words), indeterminate (all others). These are also shown in the 
table in per cents. 3 

l La Fatigue Intellectuelle, 288. 1898. 

2 The figures are evidently percentages of something : Binet does not say 
what. 

3 Neither of the revised columns totals 100 per cent. : Binet does not say 
why. 



84 



DIURNAL COURSE OF EFFICIENCY 



Table XXXIII. Fatigue — Measured by Dictation Exercises. 



Biiiet, after Sikorsky. 


Binet, revision after Sikorsky. 


No. of Class. 


9 A.M. 


3 P.M. 


Per Cent. 
Difference. 


Kind of Error. 


9 A.M. 


3 P.M. 


Class 1 
" 2 
" 3 
" 4 
" 5 
" 6 


123.5 
121.5 

72.4 
66.5 
61.4 
45.7 


156.7 
145.3 

102.8 
94.2 
81.0 
80.0 


+ 33.2 

+ 23.8 
+ 30.4 
+ 27.7 
+ 19.6 
+ 34.3 


Phonetic. 
Graphic. 
Psychic. 
Indeterminate. 


62.6 % 
8.9 % 
4.5 % 
6.0 % 


77.3 % 
11.3 % 

8.9 % 
11.9 % 



This table interprets itself. The differences in efficiency are seen 
to be very large, uniformly so, and can leave no doubt as to the cor- 
rect inference. But still greater differences were found by Friedrich 
with a class of 51, averaging ten years of age. 



Table XXXIV. 



Fatigue — Per Errors in Dictations- 
Friedrich. 



-Binet, after 





*<" . 


u . 


C . 


U to 


(H~ . 


_ j 


h 

3 


U 


tn~ . 


^r . 






s a 


s el 


3 a 


3 fl 


3 S 


o 




3 P 


3 a 






O O 


o O 


o 3 


o o 


o o 


2 




O O 




03 

3 




«i 


SI 


2* 


3* 




^ a, 


- * 




















« M 




Sh 


u <x> 


Kg 






* g 


t-i ° 


h 


h a 




Kg 


a 


« w 


2# 


£& 


2« 


2« 

3h" 


.2 


2 ^> 


2« 


2tf 


n 


<° 


<t~ 


<i© 


<< cq 


<JTH 


<-o 


m 


. <5 


-^ rt 


<JO 


45 


70 


123 


158 


112 


166 


184 


65 


152 


109 


185 



These figures serve to show the effect of recreation periods, as 
well as the gradual increase of fatigue. 

The Ebbinghaus 'method of combinations' was used by its author 
in 1897, 1 in extensive tests on school children of five grades, before 
the first hour and after each of the next five. Passages with words 
skipped were given to the pupils to fill in and the results were scored 
in number of spaces filled and number of errors made. He found, 
with few exceptions in any grade, a gradual increase of errors till 
noon, a recovery, then another drop in ability. The youngest ones 
fatigue most rapidly, as shown by the number of mistakes. This 
seems to be the typical curve for children under work conditions. 

Mathematics, considered hardest of primary studies, has naturally 
been much employed as a fatigue test. Addition or multiplication 
was used for more or less extensive diurnal tests by Oehrn ('89), 
Burgerstein ('91), Laser ('94), Schulze ('95), Amberg ('96), Fried- 
rich ('96), Kemsies ('96), Ebbinghaus ('97), Rivers and Kraepelin 
('97), Roemer ('99), Thorndike ('00), Kraepelin ('03), Ellis and 
Skipe ('03) and others. The results as a whole tend to show a de- 



1 ' Une Nouvelle Methode d'Appreciation des Capacite Intellectuelle,' Rev. 
Sclent., 4 e S, 8: 424-430. 1897. 



CAUSAL FACTORS IN DIURNAL EFFICIENCY CURVE 85 

crease of ability in children at the periods just mentioned. Thorn- 
dike's results 1 present a striking contrast to those of the majority, 
as to both adult and child students, and for that reason will be given 
more attention. His chief object was to test ability to do mental 
work before and after periods of hard mental exercise. His study 
comprises four separate articles. 

His first article deals with mental fatigue in adults. First, men- 
tal multiplication of numbers of several places was used as a test 
on three subjects for four days, two trials in the morning, and two 
at night after from seven to twelve hours' work. The results re- 
ferred to the night period were : for subject I., greater speed, less 
accuracy; for subject II., greater speed, greater accuracy; for sub- 
ject III., greater speed, less accuracy. "In all cases feelings of 
fatigue were reported at the start of the later experiments." 

Next, addition was used — twenty numbers of five figures each — 
with two subjects. They both did better before the day's work. 
These results are based on about ten before-work and ten after-work 
trials, but nineteen different days are employed. This looks like 
another case of the kind already frequently mentioned, in which 
every period concerned is not represented in each day's records used 
in the results. 

Then he investigates the influence of mental work of a particular 
sort on ability to do the same sort of work. On the whole, there 
was improvement in rate and accuracy at the second period. He 
concludes that incompetency does not come in proportion to the work 
done. "The decrease in energy does not have enough influence to 
outweigh the influence of practise. There is no pure feeling of 
general mental incompetency." The feelings of fatigue, as far as 
present, were not measures of ability. Confusion exists in experi- 
mental investigations between lack of desire and ability to do work. 

His second article treats of mental fatigue in school children. 
First, multiplication was employed with 750 Scranton and Cleveland 
school children, 375 being tested before the morning session and 375 
at the end of the afternoon session. It was found that the later 
students did 99.3 per cent, as much work as the earlier; made 103.9 
per cent, as many mistakes ; and had 114 per cent, as many bad papers. 
Other tests in spelling and memory showed little or no diminution in 
ability in the afternoon. It is seen that there is here some agree- 
ment with the results of Rice's examinations of children. Of the 
child's ability to do mental work after a half or whole school day, 
Thorndike says, however, that 'he is just exactly as able,' and that 
boredom is accountable for 95 per cent, of the apparent fatigue in 
'Mental Fatigue,' Psych. Rev., 7: 4GG-482, 547-579. 1900. 



86 DIURNAL COURSE OF EFFICIENCY 

schools during the day, while good teaching is the cure. His peda- 
gogical inferences should be read in their entirety to get the full 
force of his contention. His conclusions seem to the present writer 
to be in the right direction but rather too extreme. 

The third article deals with fatigue of special functions in adults 
— marking out words that contained the letters e and t- estimating 
small areas for several hours; memorizing series of numbers; cor- 
recting examination papers; assorting catalogue cards. He finds 
little fatigue evidenced by the single results, but they give one a 
somewhat different impression when considered as a whole. One 
thing is obvious, namely, the quantity of the work is much more 
likely to be sustained than the quality. This appeared also in the 
first set of experiments and is quite in harmony with the outcome 
of my own experimentation. It is possible that irregularity and 
inaccuracy of functioning are better, because more refined, indica- 
tions of fatigue than diminished quantity, though actually the two 
groups of phenomena are not to be separated. 

He takes up the question, in the fourth paper, as to whether 
physical fatigue is a legitimate measure of mental fatigue, and con- 
cludes that it is not. Other data in this direction were adduced 
above. 

The ground covered by Thorndike's work was extensive, though 
the series of tests were often short ; there will perhaps be general 
agreement with his conclusion that, judging from the evidence ad- 
duced, the amount of late-day inefficiency, due to fatigue, is less 
than is usually assumed and than one might expect by consulting 
one's feeling only. 

Memory and association in various forms have been favorite 
methods for determining mental fatigue; figures, nonsense syllables, 
words, objects, forms, colors, etc., have been used as materials for 
the tests. It is undesirable to attempt expression of the results of 
all these investigations, and the same may be said of the outcome of 
a variety of minor forms of fatigue tests. There are few authors 
worthy of note who do not accept the idea that ' fatigue ' is present in 
school children before the end of both day sessions, and that recesses, 
diversions, etc., produce marked improvement of ability. 

Schuytens 1 is one of these few. With a class of boys and one of 
girls, about eleven years old, he found a great inferiority of afternoon 
work in memory when the first test was given in the morning, but 
just the opposite when the first was given in the afternoon and the 
second the following morning. His figures give percentages of 

1 ' Sur les Methodes de Mensuration de la Fatigue chez les Ecoliers,' 
Archives de Psych., 2: 321. 1903. 



CAUSAL FACTORS IN DIURNAL EFFICIENCY CURVE 87 

efficiency as follows: (1) girls, 62.6 a.m., 55.1 p.m.; boys, 57.9 a.m., 
35.0 p.m. (2) girls, 77.5 p.m., 69.6 a.m.; boys, 64.0 p.m., 58.1 a.m. 
He concludes that the first experiment on children is always the 
best and must be eliminated before results are comparable, and that 
this is due to fluctuations of interest and not to afternoon fatigue. 
The pedagogical suggestion here is quite similar to that of Thorn- 
dike above. 

Opinion still remains rather diverse as to the best hours of school 
opening and closing ; the exact number, position and length of recita- 
tion and recess periods ; whether diversity of occupation, gymnastics, 
etc., furnish real relief and to what extent; amount of home study 
desirable, and other matters of less importance. These questions 
will scarcely be solved by investigating fatigue alone, the causal 
factors being more diverse and complex than that term technically 
covers. A proper line of effort for the practical educator is not to 
study fatigue less, but to make fewer assumptions as to its presence 
and amount, and to study just as conscientiously the other causes 
of temporary mental inability. 

After thus covering the accomplished work of this field, it re- 
mains to decide how much the diurnal course of efficiency is regularly 
affected by this very important factor. 

Joteyko 1 considers fatigue a means of defence of the organism, 
operating in three ways: (1) it produces paralysis of the nerve 
terminations as an immediate, physiological defence; (2) the traces 
left by the unpleasant sensations tend to ward off similar returns — 
are a preventive, psychological defence; (3) while as a consecutive 
defence it renders the organism more resistant to fatigue. The last 
suggests Binet's assertion 2 that "even a book could be written en- 
titled 'Necessity of Fatigue for Physical and Mental Hygiene'." 
In any event, fatigue lowers the expenditure of energy by intro- 
ducing more inefficient performance. This is true of physiological, 
sensory and mental functioning. Its approach should, therefore, 
herald a diminished motor force, speed and control; a lessened sen- 
sory discrimination; and a reduced mental speed, regularity and 
accuracy. This being granted, the first and perhaps most obvious 
thing about fatigue in relation to our problem is that it does not 
affect all our functions simultaneously or evenly, yet it is sometimes 
discussed as if it did. This may partly be ascribed to its confusion 
with feelings of fatigue, which seem to us subjectively to cause a 

1 ' La Fatigue eomme Moyen de Defense de l'Organisine,' C.R., IV. Cong. 
Int. de Psych., Paris, 230-231. 1901. 
2 Binet et Henri, op. tit., p. 302. 



88 DIURNAL COURSE OF EFFICIENCY 

general and pronounced decline of all our capabilities. But the 
distinction between them is imperative because the difference is real. 

IV. Inertness and Nervousness 

The distinction between fatigue and inertness, referred to above, 
needs here to be recalled and emphasized. It may be thought that 
the introduction of this term in a technical sense is a needless sub- 
division of terminology. But inertness is as distinct from fatigue 
proper as weariness is; neither is it the same as the latter, as some 
German writers have assumed. It differs from fatigue in that there 
is not present, nor could there conceivably be under the given condi- 
tions, any cell decomposition, clogging, poisoning or other histological 
characteristic of the purely fatigued cell. It differs from feelings 
of fatigue in that it has a different physiological basis and can not 
be so thoroughly eliminated by introduction of interesting or 'rein- 
forcing' stimulations of any sort. It may be, and apparently often 
is, accompanied by feelings similar to those of fatigue, though less 
unpleasant. As already intimated, the condition as a whole may be 
likened (not histologically) to that of a well-advanced convalescent 
who suffers no pain or disagreeable affections, but is simply weak 
and may be feeling well. Cowles 1 calls cases of early morning, 
relative inefficiency 'pathological fatigue,' but their occurrence is 
much too common and apparently normal for that to be wholly ac- 
ceptable. Wagner 2 also calls them the same, in reference to skin- 
insensitivity, but the writer is inclined to the other view, save as to 
particular cases. Inertness is a condition of not being wholly waked 
up and warmed up, and is normal after sleep or inactivity. 3 

Inertness may be considered a condition of under-stimulation ; 
obversely, nervousness is a condition of over-stimulation — a sort of 
excessive 'warming-up'. However caused — whether by mere excita- 
tion, by feelings of fatigue, by disease or otherwise — there can be 
no doubt that nervousness acts concomitantly with fatigue in setting 
the limit to efficiency in certain kinds of mental work. Other kinds, 
as referred to in discussing the authors, seem benefited by a mild 
amount of it. The same things may be said about other human 
employments, some being favored by nervousness — especially those 

1 Neurasthenia and its Mental Symptoms, Boston, 1-104. 1891. 

2 Unterricht u. Ermildung, Berlin, 1-134. 1898. 

s The repugnance experienced, by so many people, to reassumption of their 
week-day toils, on Monday, after a day ©f rest (?) is due, in part at least, to 
some such a deadening by inactivity. ' Blue Monday ' instances getting into 
harness again after a ' let-down.' The true psychology of stretching and of 
gaping would also shed light here. 



CAUSAL FACTORS IN DIURNAL EFFICIENCY CURVE 



89 



requiring speed, as exemplified by the factory employees — and some 
impaired, as noted in the discussion of various accuracy tests. 

The extent to which the inefficiency of the later part of the day 
is due to weariness and how far to real fatigue and nervousness is a 
hard question to solve. Objective tests, whether of the 'spurt' or 
prolonged type, probably give a better idea of the real capacity at 
any period than do our subjective feelings, while the latter seem 
more indicative of what we are likely to do under ordinary condi- 
tions. Effort was made to get some data on this matter by having 
different people draw daily curves of their efficiency as estimated 
by their feelings, but only a few records were secured. In Fig. 4 
are shown such curves for five of the subjects used in the author's 
experiments. 



AJVL 



F>,M. 




6 8/0/22 <? 6 S /O /2 
Fig. 6. Diurnal Curves of the Subjective Feeling of Efficiency. 



These curves would be more interesting for comparison with the 
actual records of the subjects if the operation of comparison were 
less intricate. The purport of the paper thus far has been against 
indiscriminate lumping of physical or mental functions in order to 
get some sort of curve of ' general ability '. The tests and test periods 
were too few, in most cases, to make it possible for separate curves 
to be reliably drawn for rate, accuracy, strength, etc., and this was 
not attempted, save in the rough way indicated by the following 



90 DIURNAL COURSE OF EFFICIENCY 

general statements. Subject II. seems actually to follow his curve 
the closest, and III. the least closely, relatively, to the greatest number 
of tests. On the whole about 60 per cent, of the actual curves might 
be said to resemble the affective ones rather closely. Strength seems 
most inversely, and addition most directly, correlated with the feel- 
ings, though the number of common tests is too small to make this 
very reliable. 

The afternoon drop in all these curves and the high night feeling 
of ability, shown in all but one, appear to be rather characteristic of 
students. Five professors and a number of students have told the 
author that this is a true expression of their feelings. Much better- 
ment occurs where there is need of 'buckling down' to some par- 
ticular task in the afternoon, but to what degree this takes place or 
is possible is a question. 

This matter of the relations between what one can do, is likely 
to do and does do is one upon which a large quantity of curves, like 
those presented above, would probably shed some light. In addition 
to the 'general tendencies' in these curves, to which attention has 
been called, it is seen that all of the five estimate themselves at a low 
figure for the first period. This is strictly in accord with the fact 
disclosed by their actual tests. Here feelings of fatigue apparently 
are present. However, the morning feeling, after introspective 
analysis, is connected by four of them — the other being uncertain — 
rather directly with some physical basis, while that of the afternoon 
is referred to one more distinctively mental. Though the distinc- 
tions here are vague, these few cases suggest that there are 'feelings 
of inertness ' just as there are ' feelings of fatigue '. Theoretical psy- 
chological principles also lead to this supposition, if it is true that 
inertness as described is a fact. From the evidence in hand the 
relative importance of these various factors can not be satisfactorily 
judged. 

V. Sex and Age. 

It has been pointed out frequently in the preceding pages that 
there seems to be in adults a tendency for females to reach an earlier 
maximum of ability than males, and children than females. The 
greater influence of fatigue and weariness with both women and 
children is apparent, and the recovery after meals and reactions 
seems also greater. 1 

1 Of 200 persons replying to a questionnaire sent out by Partridge (' Second 
Breath,' Ped. Sem., 4. 1896-1897), 66 reported experiences of physical 'second 
breath ' — recuperation with slight or no rest, after exercise — of whom 30 were 
females and 36 males; 102 reported mental 'second breath,' of whom 89 were 
females and 13 males. 



CAUSAL FACTORS IN DIURNAL EFFICIENCY CURVE 91 

This running down in children, as far as it is a fact, is not due 
to uninteresting teachers wholly, nor yet to hard work, but is rather 
independent of occupation, if the following is a correct interpreta- 
tion of results obtained by Rivers and Kraepelin 1 from experiments 
on the effect of intervals of rest upon work ability. Beginning at 
8 a.m., the subject was required to spend four half-hour periods in 
adding, each such period being followed by a half-hour period of 
rest. Of the three days' results that were used, all show increase of 
ability after the first pause, but only one day shows this after the 
second pause, and none after the third. The inference was that the 
first rest was enough to effect complete recovery from the fatigue 
of the preceding addition; the second was only partially enough; 
and the third was quite inadequate. But, if there was entire re- 
cuperation after the first half hour's work, unless a naturally de- 
teriorating disposition intervened, the second and third rests should 
have been quite as effective as the first. The same thing comes out 
even more positively in a second series of experiments, similar in 
every way to the former save that an hour's rest followed a half 
hour's work. In this case the greatest efficiency was again mani- 
fested after the first rest and thence there was a steady decline, 
though the first half hour 's point of deficiency was not again reached. 
This was taken to mean that the practise effect and momentum were 
lest in the large rest intervals, while the fatigue effect was too great 
to be overcome after the second addition, just as in the other series. 
It is, however, very improbable that the fatigue effect would last over 
an interval long enough to destroy the practise effect. What prob- 
ably took place was a normal decline that was merely hastened by 
the special fatigue of the tasks imposed and by a growing lack of 
interest. Children lose in efficiency much more readily than adults, 
but also recuperate more rapidly. The reason lies in the facts that 
they enter into what natively interests them with more fatiguing 
zeal than adults, while, on the other hand, they are more prone than 
adults to surrender to their feelings of fatigue where their interest 
is not so intimately engaged. To a lesser extent the same is true of 
women. 

VI. Brief Summary. 

It has been urged that the night-day rhythm imposes on us cor- 
responding periods of sleep and activity whose recurrence is the 
basic condition of diurnal periodicity in efficiency. The sleep effect 
is prolonged beyond waking as a sort of inertness which is neither 
real fatigue nor merely feelings of fatigue, but is usually accom- 

1£ Ermudung u. Erholung,' Psych. Arbeiten, 2: 627-678. 1896. 



92 DIURNAL COURSE OF EFFICIENCY 

panied by feelings of inertness or of fatigue, or both. It is pro- 
nouncedly manifest in muscular abilities, especially strength, but 
seems less and less apparent and persistent as the mental field is 
entered. The process of growing awake is accelerated by a progres- 
sive increase of sensorial responsiveness which successive stimuli, 
acting cumulatively, seem to entail on the organism, and this con- 
tinues till a normal limit is reached or some modifying factor inter- 
feres. Chief among such factors are personal habits, meals, fatigue 
and feelings of fatigue, nervousness, sex and age. The effects of 
habits (physical, social, mental, etc.) and of meals vary according 
to the particular case, but generally speaking they institute a recur- 
rence of like conditions, effective even during the temporary discon- 
tinuance of the habits. Eeal fatigue sets the limit to the absolute 
maximum of efficiency, but it is probable that feelings of fatigue 
have more to do with the curve of our ordinary, practical efficiency 
— of what we actually accomplish. It appears that women expend 
themselves proportionately more energetically than men in things 
in which they are intimately interested, and at the same time that 
their feelings of fatigue are stronger and exercise a more deterrent 
influence where their personal interests are not so immediately con- 
cerned. This seems increasingly true of children, and hence we find 
in these two groups a corresponding inclination to an earlier maxi- 
mum of efficiency, but complicated by a more facile recuperation. 



E. CONCLUSION 

The attitude of the author in this paper has been conservatively 
favorable to the idea of a few, broad diurnal variations of a rather 
general nature, coexisting with more numerous and intensive varia- 
tions in individuals. Such, in fact, seems to be the outcome of the 
investigation and of the collation of data from other sources. Scien- 
tifically, the application of such a conclusion is both direct and valu- 
able. For its truth carries with it the suggestion that psychological 
and physiological investigators would be obliged to take into con- 
sideration more conscientiously than heretofore the fact of period- 
icity in individuals. Comparative experiments should not be per- 
formed indifferently at varying times of different days, if exact 
results are to be expected. Not only are some variations of ability, 
between certain periods, as great or greater than sex differences in a 
homogeneous group, but some of the latter may possibly be accounted 
for by reference to the differences between the diurnal cycles of the 
two sexes. 

When it comes to making a more practical application of the 
fact of periodic variation, we become principally interested in the 
quantitative value of the differences. If only a slight difference 
occurs between the extremes of diurnal efficiencies, we should doubt- 
less take no account of it in any voluntary ordering of our lives. 
Even in the event of a larger difference, our peculiar subjective 
organization makes it a question worth asking by each person whether 
the reduction of the inefficiency at any period should be attempted, 
since such incompetency at one period may often insure, in his in- 
dividual case, better subsequent work than otherwise would have 
been performed. Many writers are on record as being unable to com- 
pose at certain times, perhaps for days, weeks or even months. The 
explanation of these periods of enforced inactivity furnishes a good 
problem for investigation, but one can scarcely disbelieve that they 
contribute, in some way and degree, to the betterment of future 
functioning. There is here a practical problem for every one to 
solve in his own case; and at the same time a problem of general 
scientific interest. 

A general expression of the quantitative differences between the 

efficiency at different times of the day could be given, if records for 

15 days— 10 periods each— of 100 individuals, were available in a 

number of the motor and mental activities. The figures of the wire- 

7 93 



94 DIURNAL COURSE OF EFFICIENCY 

stitchers (p. 35) offer material for illustration. The average of the 
maximal and minimal number of magazines handled by an operative 
approximates her mean speed per day. Calculation shows the sub- 
jects to be, at the minimal period, below their respective averages, 
by the following per cents. : 5, 6, 4, 13, 7, 6, 7, 3. This, of course, is 
very rough, as it takes no account of the reliabilities of the various 
figures; but as far as it goes, it indicates that in the employment of 
adults in manual labor one might expect the early morning, where 
the minima mostly occur, to return in production about 6 per cent, 
less than the day's average, and from 10 to 12 per cent, less than at 
the best period. Allowance must, however, be made for the fact 
that, if the women had worked every night, instead of alternate ones 
only, these results would doubtless be somewhat altered. 

Would it then be better for the work-day to be shortened at the 
morning end rather than, as customarily, at the night end 1 ? It 
might, if there were any guarantee that the employees would keep to 
their same hours of rising; otherwise no improvement would be ex- 
pected. The 'warming up' must be effected, whether it be early or 
not, and late sleep usually retards the process. Even if it were 
practicable for an employer to 'exercise' his workers vigorously for 
an hour before starting them on pay-time work this would scarcely 
prove profitable to him, because of the involved expenditure of 
energy needed in their actual work; and it would only be profitable 
in case of a shortened day and time-work. In piece-work, since pay is 
dependent solely upon the amount done and not upon the time con- 
sumed, there is nothing in the problem of diurnal rhythms that would 
interest the employer, save when the rapidity with which he might 
want a special job finished is in question. Even in this instance, the 
application would be limited to cases in which extra 'hands' were to 
be secured for the occasion— that is, they could be hired only for their 
periods of high efficiency; this would hold good also for part-time 
time-workers — because any reassignment of his 'regulars' to such 
special 'rush' work would be governed by the actual amount of work 
required to get out on time the regular jobs on hand. But it 
would be of interest to the employee, if the extra exercise could be 
endured, since it would enable him to start in at a rate which he 
must else more slowly attain. Beyond this, there seems no practical 
industrial application of any consequence. 

As before stated, the practical value of investigations of this 
question has perhaps most particular reference to school life. Most 
of them have been carried on with this in view : whole curricula have 
been suggested, ordered in accordance with the results of different 
researches. It will be clear to the reader of the preceding pages 



CONCLUSION 95 

that such curricula rest on insecure bases as yet, but that the em- 
pirical work has not, therefore, been without value. The main result 
of the present research, in this connection, consists in restablishing 
a principle already well known in the pedagogical field, but not well 
enough recognized. Kraepelin's thought that 'the present arrange- 
ment of school programs makes it a necessity to have tedious teachers 
in whose classes the pupils may rest themselves by inattention' may 
have some truth in it, but it is much more worth noting that the 
most wholesome and economical development of the pupil makes it 
necessary to have interesting teachers in whose classes the pupils 
may rest themselves by a more ' f rictionless, ' and develop themselves 
by a more fully utilized, expenditure of energy. The feelings of 
fatigue, to which they are often exposed, are more deadening intel- 
lectually than the real fatigue of a day's interesting work and, in 
addition, do not represent actually growthful exercise of the func- 
tions concerned. 

As far as older people are concerned, this principle can be ap- 
plied somewhat similarly. The feelings of languor and weariness, 
to which one may become more subject as he indulges in them, might 
more and more be made to disappear, as far as they are not due to 
structural defects or any constant and uncontrollable cause, if a 
definite course of activity were consistently pursued in spite of them. 
In this case, a sort of artificial interest ultimately replaces the native 
spontaneity of the children, and institutes a condition of less ex- 
penditure of energy in performing the given act at the given time. 
Kraepelin is of the opinion that 'every human being has his own 
peculiar way of work, which usually shows itself regularly in the 
same manner during every working period.' That is too sweeping, 
but it is probable that the older one grows the more it tends to be- 
come true, because habits become more firmly ingrained. 

Perhaps a few remarks should be made as to the existence of so- 
called 'morning workers' and 'night workers.' When the evidence 
of the preceding pages is reviewed, especially that concerning stu- 
dents and authors, their existence can scarcely be questioned. The 
Germans have long accepted the matter as settled and Kulpe can be 
cited as a splendid example of the fact involved — as a night worker. 
Here again the quantitative aspect — how many the persons and how 
much the difference — are the all-important practical considerations, 
and here again it must be said that ample data for their determina- 
tion are not as yet at hand. 

The range of the results set forth in this paper has been so ex- 
tensive that a definite impression as to where their main tendencies 
lie may still be lacking. For that reason a method was diligently 



96 DIURNAL COURSE OF EFFICIENCY 

sought by which they could be presented, either tabularly or graph- 
ically, in such a way as to indicate this in small scope. However, 
when one attempts properly to weight data, obtained from diurnal 
periods varying in number from 2 to 24 ; from various measurements 
of various activities; from subjects of varying number, age and sex; 
and under other varying conditions — the task is found to be quite 
hopeless. This is not strange, however, considering that even the 
'laws' of physics can not always be expressed in one figure or 
formula. For instance, expansion of volume by heat has several 
coefficients for solids; a constant one for gases; two for liquids, 
which only partly hold true; while water in certain phases exhibits 
phenomena contrary to the general law. Much more do individuals 
differ psychologically. After all, if all the figures in the text were 
reduced to some percentage basis, they would still be incomparable 
for this reason, that an increased efficiency of 10 per cent, in one 
case would probably not at all mean the same in reality as an in- 
crease of 10 per cent, in another function. Such a summary would 
be satisfactory in its compactness, but misleading as to fact. For 
the chief specific conclusions, therefore, the reader is referred to 
the brief summaries on pages 13, 14, 40, 69, 91, which together cover 
the whole investigation on its empirical side. 



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THE DIURNAL COURSE 
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